The West Indian Manatee (Trichechus manatus) is currently divided into two subspecies: the Florida Manatee (T. m. latirostris) and the Antillean Manatee (T. m. manatus) (Hatt 1934, Domning and Hayek 1986).  The mtDNA data (García-Rodríguez et al. 1998) and molecular data (Vianna et al. 2006) revealed a population structure with three distinctive lineages corresponding geographically with: (1) Florida, Mexico, the Greater Antilles, Central America, and the Caribbean coast of South America; (2) Mexico, Central America, and the Caribbean coast of South America; and (3) NE South America from Guyana to Brazil. Evidence exists for viable hybridisation with T. inunguis near the mouth of the Amazon River, Guyana, French Guiana, and possibly Suriname (Lima et al. 2019).

Recent cranial and chromosomal geographic variation data from Antillean manatees in Brazil show morphological discontinuity and chromosomal divergence within T. m. manatus and the Brazilian population south of the Amazon. These data suggest that the current taxonomy of T. manatus needs to be revised (Barros et al. 2016).

As this Red List assessment was being submitted for publication, we were made aware of a paper by Mignucci-Giannoni et al. (2024) that proposes to standardise the vernacular names for Trichechus manatus and subspecies across five languages. The proposed common names in English are: American Manatee instead of West Indian Manatee for T. manatus; Florida Manatee as it currently is used for T. manatus latirostris; and Greater Caribbean Manatee instead of Antillean Manatee for T. manatus manatus. We have left the existing common names in this assessment, as they are well-established and associated with various federal and state legislation, but recognise that there may be support to change those names in the future.   

 

The West Indian Manatee is comprised of two subspecies, the Florida Manatee (Trichechus manatus latirostris) in the United States and the Antillean (Greater Caribbean) Manatee (T. m. manatus), whose range extends from Mexico and the Caribbean Sea to Brazil. The quantity and quality of population information differs tremendously between the two subspecies, and across countries within the species’ range. The species is listed as Vulnerable under criterion C1 because the number of mature individuals is likely to be less than 10,000 (based on combined population estimates for the Florida and Antillean (Greater Caribbean) subspecies) and there is a reasonable chance that the overall population could decline by at least 10% over the next three generations (estimated at ~60 years) as a result of both habitat loss or degradation and anthropogenic factors. The minimum number of mature individuals in the species as a whole is estimated to be 8,197, with a best estimate of 11,328; most of those animals were found in the United States: 69.4% of the minimum and 57.2% of the best estimate of the species' total abundance (see Supplementary Material Table S1). Given the large uncertainties in most of the country-specific abundance estimates, we have adopted IUCN's recommendation to take a precautionary but realistic approach in evaluating the population against the IUCN Red List Criteria (IUCN 2012, p. 23–24). The Florida Manatee and the Antillean (Greater Caribbean) Manatee are listed as Vulnerable and Endangered, respectively; see the subspecies accounts for detailed explanations and justifications for these Red List status assignments.

The West Indian Manatee (Trichechus manatus), recently proposed to be called the American Manatee (Mignucci-Giannoni et al. 2024), has an extensive range along the coastal region of the tropical and subtropical Western North Atlantic Ocean and Western South Atlantic Ocean, including the Caribbean Sea. The species inhabits riverine, lacustrine, lagoon, and coastal aquatic systems from the southeastern United States of America through Mexico, Central America, and to northeastern Brazil in South America. Manatees are found on the islands of the Caribbean Sea, including the Greater Antilles (e.g., Cuba, Hispaniola (Haiti, Dominican Republic), Jamaica, and Puerto Rico). Over the past three decades manatee presence has been confirmed in the coastal waters and rivers of at least 19 of the 42 countries with current and historical records (see Supplementary Information Table S1). For countries with current resident populations of manatees, manatee occurrence and distribution are described below in alphabetic order by country, grouped into four broad regions. See the distribution map to visualise range and distribution, and the associated Country of Occurrence table codes for information on presence, origin, and seasonality for each segment of the distribution.

Manatees in the United States of America (T. manatus latirostris)

Florida Manatees are found in the United States of America (USA), but a small number have recently reached the Bahamas and have taken up residence there (see below). Their year-round distribution in the USA is restricted to peninsular Florida because they need warm water to survive the winter. During the warm season (March or April through October or November, depending on latitude and weather patterns in a given year), manatees disperse throughout the coastal waters, estuaries, and major rivers of Florida and some migrate to other southeastern coastal states, particularly Georgia and Alabama (Deutsch et al. 2002a). Along the Atlantic coast these states include Georgia, South Carolina, North Carolina, and Virginia; a small number of manatee sightings have occurred along the mid-Atlantic coast as far north as Massachusetts. Along the Gulf of Mexico coast west of Florida, some manatees regularly migrate to Alabama during the warmer months and others are occasionally sighted in Mississippi, Louisiana, and as far west as Texas. One manatee was even documented near Memphis, Tennessee, over 1,000 km up the Mississippi River from New Orleans, Louisiana (Deutsch et al. 2022a). The exact delineation of range limits is somewhat arbitrary, but based on available sighting reports (e.g., Fertl et al. 2005, Cummings et al. 2014, USGS unpublished data), we have placed them in the mid-Chesapeake Bay on the Atlantic coast and Corpus Christi, Texas on the Gulf of Mexico coast.

Florida Manatee range constricts dramatically in the winter season (December to February) when manatees seek shelter from the cold at a limited number of warm-water sites or areas in the southern two-thirds of Florida. These sites include seven principal power plant thermal outfalls (four on the Atlantic coast, three on the Gulf of Mexico coast) and four major artesian springs (Volusia Blue Spring, Kings Bay springs at the head of Crystal River, Homosassa Springs, and Warm Mineral Spring) that are frequented by a large proportion of the manatee population during winter (Laist et al. 2013). In addition, manatees use several other springs and a number of passive thermal basins where warmer water temperatures persist as ambient temperatures in adjacent bays and rivers decline during cold fronts.

Manatees in Mexico and Central America (T. manatus manatus)

Belize:
Manatees are present in the main rivers, lagoons along the coast, Drowned Cays, and the Turneffe Atoll, from the Hondo River on the border with Mexico to Sarstun River on the border with Guatemala (O´Shea and Salisbury 1991, Morales-Vela et al. 2000, Lefebvre et al. 2001, Auil 2004, Edwards et al. 2014). Many manatees frequently use the Placentia, Indian Hill, Southern lagoons, Drowned Cayes, and the Belize River (Morales-Vela et al. 2000, Auil 2004).

Costa Rica:
Manatees are still present in most of their historical range (UNEP 2010, Jiménez 2012). In the 1990s, the main manatee habitats included the north zone (San Juan and Colorado Rivers), the northeast coast (Tortuguero River and the Tortuguero National Park), and the southern coast (Sixaola and Carbon Rivers). Since 2010, there are new reports of recurrent manatee presence in the coastal marine habitats from the Sixaola River, Gandoca area to Cahuita National Park (Fundación Trichechus pers. comm. 2018). The Saxiola River is a manatee priority zone on the border with Panama. Also, the rivers and creeks on the border with Nicaragua are critical areas for the species.

Guatemala:
Lago de Izabal, Bahia de Amatique, Sartún River, and El Golfete are the main areas of manatee presence in the country (Quintana-Rizzo 2005, UNEP 2010, Machuca and Corona 2019, Quintana-Rizzo et al. 2023). The two most important habitats for the species are the protected areas of Refugio de Vida Silvestre Bocas de Polochic, located in Lago de Izabal, and Bahía La Graciosa, located in the Refugio de Vida Silvestre Punta de Manabique in Bahia de Amatique (Quintana–Rizzo 2005, Quintana-Rizzo and Machuca 2010, Quintana-Rizzo et al. 2023). El Estor, Los Murciélagos, and Punta Brava are important sites in the Lago de Izabal (UNEP 2010).

Honduras:
Manatee presence is in most major rivers, lakes, and lagoons along the coast of Honduras, including the Bahía de Omoa, Punta Sal, Laguna Thompson, and the Motagua, Monje, Ulua, Chapagua, and Aguán rivers, as well as on the eastern coast at La Mosquitia (González-Socoloske et al. 2011). The Refugio de Vida Silvestre Cuero y Salado and its rivers (Cuero, Salado and San Juan), on the northern coast provide some of the most important manatee habitats (González-Socoloske et al. 2011) in the country.

Mexico:
Manatees are extant in riverine and coastal habitats of the Gulf of Mexico and the Caribbean coasts, from the Tecolutla River in Veracruz to Chetumal Bay in Quintana Roo and Hondo River on the border with Belize (SEMARNAT 2020). In the Gulf of Mexico, the freshwater systems comprise most of the manatee habitat (Jimenez-Domínguez and Olivera-Gómez 2014), including the Alvarado Lagoon in Veracruz, the lower basins of the Grijalva and Usumacinta rivers in the states of Tabasco, Chiapas, and Campeche (SEMARNAT 2020), and the rivers of Palizada, Candelaria, and Chumpan in the Chiapas and Campeche states (Ladrón de Guevara et al. 2019). Two recent vagrants have been documented in Tamaulipas, including one young manatee sighted in the Pánuco River in 2018 and one adult sighted in the Ejido Punta de Piedra (24oN) in 2019 at 172 km from the border with Texas (B. Morales-Vela pers. comm. 2020). A recently confirmed case of manatees from Florida occurred in Tamaulipas state on June 9th, 2022, in the Panuco River, where a group of four adult manatees included one with scars that were used to confirm his identity from Florida (Morales-Vela et al. 2023).

On the Caribbean coast of the Yucatán Peninsula, most manatees are present in the lagoons and estuaries of the reserves of Yum Balam, Sian Ka’an, and Chetumal Bay, including the Hondo River on the border with Belize (Morales-Vela and Olivera-Gómez 1997, Morales-Vela et al. 2000, Corona-Figueroa et al. 2020, Callejas-Jimenez et al. 2021, Morales-Vela and Bahena-Basave 2023). In addition, manatees use the barrier reef, artesian springs known as “Cenotes,” and small inlets or “Caletas” that are found along the coast from Playa del Carmen to Tulum and that continue to Xcalak on the border with Belize (Morales-Vela and Olivera-Gómez 1997, SEMARNAT 2020).

Nicaragua:
Manatees are still present in most of their historical range along the Caribbean coast, the main rivers, and coastal lagoons of Nicaragua, and up to 60 km inland in large rivers such as San Juan, Wawa, and Kunima (Jiménez 2012). There is abundant pristine manatee habitat on the northeastern coast with extensive wetlands. The southern coast has rivers, creeks, and small lagoons with abundant emergent and floating vegetation (Jiménez 2012).

Panama:
Manatees are present in two main regions of Panama. The first region is on the western coast in the San San Pond Sak wetland (Guzman et al. 2017), specifically in the Sixaola, San San, Changuinola, and Negro rivers (Lefebvre et al. 2001). The second region is Lake Gatun in the Panama Canal Watershed (Muschett and Vianna 2015). This population in Lake Gatun is the product of a 1964 introduction of nine West Indian Manatees translocated from Bocas del Toro, and one Amazonian Manatee (Trichechus inunguis) translocated from Peru to the Chagres River at Gamboa to control aquatic vegetation in the Canal (MacLaren 1967, Montgomery et al. 1982). There are also reports that animals from the Canal had reached Miraflores Lake in 1979 and 1980, one lock away from the canal entrance to the Pacific Ocean (Montgomery et al. 1982). Recent reports also exist for the southern part of Bocas del Toro in the Damani-Guaribiara wetland (K. Ruiz pers. comm. 2020). Along the east coast, there appears to be a gap in suitable manatee habitat where no manatee sightings have been reported, which could serve as a geographic barrier that separates the manatee populations of Panama and Colombia (Díaz-Ferguson et al. 2017).

Manatees in South America (T. manatus manatus)

Brazil:
The manatee is present from Amapá, on the northwest coast, to Alagoas on the northeastern coast (Luna et al. 2021, Meirelles et al. 2022), with three discontinuous areas: on the east coast of the state of Maranhão, from Lençóis Maranhenses to the western portion of Delta do Parnaíba (Luna et al. 2008a, 2010, 2018), in the state of Ceará, from Camocim to Fortaleza (Meirelles et al. 2018, Luna et al. 2018), and in the state of Pernambuco, from Tamandaré to Conceição beach (Luna et al. 2018). The absence of the species on the west coast of Ceará seems to be related to the lack of favorable ecological conditions (Mirelles et al. 2018), as described for the discontinued area in the bordering state of Maranhão, where there is no suitable manatee habitat on that coast (Luna et al. 2008a, 2008b).

In the northern region, most manatees have been observed in estuarine systems, followed by rivers and coastal areas (Meirelles et al. 2018). Freshwater sources significantly influence their abundance (Favero et al. 2020). Both the Amazon region of Marajó Island and the whole coast of Amapá have been described as a sympatric area for the Amazonian and West Indian Manatees (Luna et al. 2008a, 2008b; Oliveira et al. 2022). Later it was described as a hybridisation zone (Lima et al. 2019, Vilaça et al. 2019), but no evidence of this hypothesis was confirmed in a genotype analysis of multiple nuclear loci implemented by Luna et al. (2021), leaving the need for future research on the identified putative hybrids. A recent cytogenetic analysis gives evidence of the natural occurrence of hybrids between T. manatus and T. inunguis in this region (de Oliveira et al. 2022).

Colombia:
Manatees are present mainly in the riverine environment, coastal lagoons, and creeks and are occasionally present along the coast in mangrove swamps and estuaries. There are no manatee records or reports from the region of the Dibulla-Guajira desert to the border with Venezuela, a distance of almost 350 km (Debrot et al. 2022).

Three hydrological basins are essential for manatees: Atrato, Sinú, and Magdalena (Montoya-Ospina et al. 2001). The latter has been identified as one of the most important manatee areas in the country (Montoya-Ospina et al. 2001), particularly the middle and lower basins of the Magdalena River and its tributaries, including the Cauca, San Jorge, Cesar, and Lebrija Rivers, and the associated swamps of Cienega de Paredes, Zapatosa, la Rinconada, San Zenon, Guazo, Tacasaluma, Panceguita, Jegua, San Marcos, Ayapel, and Brazo del Chicagua (Castelblanco-Martínez et al. 2015; B. Aguilar-Rodríguez pers. comm. 2018). In the Orinoco River, relevant manatee populations are over 1,100 km from the Caribbean coast (Castelblanco-Martínez et al. 2009).

French Guiana:
Manatees are present along the coast, estuaries, and main rivers, including the border rivers with Brazil and Suriname (de Thoisy et al. 2003, Castelblanco-Martínez et al. 2017). There are reports of manatee sightings up to 80 km inland on large rivers such as the Oiapoque River (Thoisy et al. 2003). The Guianas coast was recently hypothesised as a zone of hybridisation between Amazonian and West Indian Manatees (Lima et al. 2019, Vilaca et al. 2019), although this hybridisation was not supported through the analysis of multiple nuclear loci (Luna et al. 2021), leaving the need for future research.

Guyana:
Historically, the northwestern coast and the area along the Suriname border were considered to have the largest number of manatees (Bertram and Bertram 1963). Some manatees lived mainly in the rivers of the coastal plain and the regions of the wet savannah. Reports from the 1980s suggest that manatees could be observed in the Baramani and Akawini Rivers. The Guiana’s coast was hypothesised as a zone of hybridisation between Amazonian and West Indian Manatees (Lima et al. 2019, Vilaça et al. 2019). However, this hybridisation was not supported through the analysis of multiple nuclear loci (Luna et al. 2021), leaving the need for future research.

Suriname:
Prime manatee habitat includes four major estuaries associated with the principal rivers of the Marowijne, Suriname, Coppename, and Corantijin and the tributaries of the Mana, Commewijne, Saramacca, and Nickerier rivers (Pool 2012, 2013).

Trinidad and Tobago:
The most recent manatee records were two carcasses found on the east coast of Trinidad, specifically one carcass that was found at the mouth of the Mitan River in the Nariva Swamp, and the other carcass was found in the northern Ortorie River (NewsDay 2012). Both sites have a historical presence of manatees (Romero et al. 2002, NewsDay 2012).

Venezuela:
Venezuela has one of the most extensive manatee habitats, but it also is one of the countries with scarce information on the species' status and distribution. The northern side of Lago de Maracaibo, Bahía El Tablazo, is one of the last confirmed sites of manatee presence (Manzanilla-Fuentes 2007). The Peninsula de Paria and and tributaries along the coast of the state of Sucre are historical sites of manatee presence (Ferrer et al. 2017). The middle region of the lower Orinoco River is a historical region of manatee presence confirmed in 2007–2008 (Aguilar et al. 2012). The Orinoco River is also an important habitat for manatees with a regular confirmed presence at least 1,000 km from the Atlantic coast (Aguilar et al. 2012) or over 1,100 km in the Orinoco region of Colombia (Castelblanco-Martínez et al. 2009).

Manatees in the West Indies (T. manatus manatus)

The Bahamas:
A very small resident population of West Indian Manatees has become established in the northern islands of The Bahamas (above 24° N, except for the Exumas and San Salvador), especially Grand Bahama, Abaco, the Berry Islands, New Providence, Andros, and Eleuthera. Knowles et al. (2016) determined that there were at least 15 manatees among the islands based on photo-identification and sighting patterns. Some of these manatees have bred and given birth in The Bahamas (Claridge 2015). Individuals have been documented through photo-identification and, in one case, from satellite telemetry to have come from both coasts of Florida (Reid 2000, Lefebvre et al. 2001, Melillo-Sweeting et al. 2011, Rood et al. 2020). We consider this to be a range extension of the Florida subspecies into the northern portion of The Bahamas.

There is no history or known origin for other manatees sighted in this vast island nation and there are likely individuals from the Antillean (Greater Caribbean) subspecies present. Historically, The Bahamas was considered in the range of this subspecies. Sightings are much less frequent in the southern portion of The Bahamas (i.e., south of 24° N), but there are some regular sightings at Long Island (James Reid, USGS, pers. comm.). The Greater Antilles are a likely source for manatees found in Great Inagua in the southernmost district of the Bahamas (Lefebvre et al. 2001), at only 88 km northeast of Cuba. Historical and recent reports of manatees from the Turks and Caicos Islands (Alvarez-Alemán et al. 2018, Caribbean Manatee Conservation Center unpubl. data) may point to those islands as stepping stones for manatees to reach The Bahamas from the south. The subspecies' boundaries shown on the range maps in The Bahamas are therefore somewhat arbitrary; further genetic and photo-identification studies will be needed to elucidate the origins of manatees found in these islands.

Cuba:
Manatees in the Cuba archipelago are present along marine coasts, estuaries, mangroves, and rivers (Alvarez-Alemán 2018). Some gaps in the distribution across the island might be related to the lack of suitable habitats due to the absence of critical ecological resources or the presence of anthropogenic activities. The Ensenada de la Broa and the Hatiguanico River in the Zapata Peninsula have manatee sites of historical and current use (Lefebvre et al. 2001, UNEP 2010, Alvarez-Aleman et al. 2018; Alvarez-Alemán et al. et al. 2022). The Lanzanillo-Pajonal-Fragoso Marine Protected Area in the Province of Villa Clara, on the north coast, also has extensive manatee habitat (Alvarez-Alemán et al. 2018). In Laguna del Tesoro in Matanzas Province, manatees were introduced on several occasions in 1964 and 1990, but their numbers in this lake have declined (Alvarez-Alemán et al. 2018).

Dominican Republic:
Manatee distribution in the Dominican Republic has not changed for 30 years (Dominguez-Tejo 2016). Manatees remain widespread along the coast and in estuarine ecosystems such as mangrove bays and rivers (Dominguez-Tejo 2019). Focal manatee areas, including hotspots, have been identified in the Monte Cristi and Puerto Plata provinces on the northern coast and the Pedernales, Barahona, and Azua provinces on the southern coast (Dominguez-Tejo 2016). Two freshwater systems, Higuamo River and Caño Estero Hondo, have recently been identified to have a year-round manatee presence, including mother-calf pairs (Dominguez-Tejo 2012, 2019).

Haiti:
Manatees are relatively rare in Haiti. From 2007 to 2013, reports were concentrated in two areas: Gonaives to Montrouis on the central coast and Jacmel to Grand Gosier on the southeast coast (Dominguez-Tejo 2019). The last five confirmed reports are from 2019, 2020 and 2021: in September 2019, a manatee was sighted in Nippes coast of the southwest coast; and in October 2019, four manatees were sighted in Anse a Foleur on the northern coast (Mignucci-Giannoni and Aquino 2020).

Jamaica:
Manatees are occasionally sighted along the southern coast of Jamaica, including the Manchester, St. Elizabeth, and St. Catherine provinces. Manatee sightings are primarily in the Portland Bight, specifically the Galleon Harbour Special Fishery Conservation Area, which is at the east of the Portland Ridge, from Milk River in Clarendon to Treasure Beach in St. Elizabeth (D. Calder pers. comm. 2020). More isolated reports have been on the north coast, namely Portland Parish in the northeast and Trelawny Parish in the northwest. The most recent confirmed manatee sighting occurred in Alligator Pond River on 18 September 2020, and in Turtle Harbour, Portland, on 6 December 2020 (D. Henry pers. comm. 2020). From 29 November to 1 December 2008, a group of manatees was sighted in St. Ann´s Bay (NEPA 2008). Three manatees were reported in the Castle Cove area of Portland two years earlier, and the other three were sighted in Montego Bay Harbor (NEPA 2013). Those observations were important because Palisadoes-Port Royal and Portland Bight Wetland and Cays were designed for Ramsar sites in 2005 and 2006, respectively, and manatees are in their list of priority species for conservation (NEPA 2013).

Lesser Antilles:
Despite sporadic manatee sightings in several islands in the Lesser Antilles over the past 30 years, there is not a consensus among the authors of the T. m. manatus assessment as to whether manatees were native or vagrant in these islands in the past. Valid arguments can be made for either position. However, the senior author (Morales-Vela), the second author (Quintana-Rizzo) and the past red list assessment (Self-Sullivan and Mignucci-Giannoni 2008) considered origin to be ‘native,’ which is how it is assigned here. In support of this decision is the consideration of valuable specific records about the historical presence of manatees in the bays of the Grand and Petit Culs-de-Sac marines and its islets at Guadeloupe Island during the second half of the 17th century. Father J.B. du Tertre wrote in 1667: “How extremely peaceful the sea is in these two Culs-de-sacs-bag. The sea is not deep there; one would not believe how many manatees, turtles, and all the other fish thrive around these islets” (du Tertre RP J.B. 1667–1671, cited in Lartiges et al. 2004). du Tertre also points out the abundance of manatees in Saint-Martin, speaking of “Culs-de-sacs which advance far into the earth and are the lair of quantities of manatees, turtles and other fish which provide food for the inhabitants” as well as in Grenada: “It is an astonishing thing to see the quantity of game, manatees, turtles, and all kinds of fish that are found there…” (Lartiges et al. 2002). The decrease would have been rapid in Martinique since Father J.B. Labat indicated in 1722, “it has become rare since the seaside became inhabited” (Labat 1732 cited in Lartiges et al. 2002). For Guadeloupe, Father J. Ballet (1894) indicated that the number of manatees had seriously decreased in the second half of the 19th century (Lartiges et al. 2002). Manatees hold a significant place in Guadeloupe's local folklore and history, particularly in the town of Lamentin, which is located near Grand Cul-de-Sac Marin. This cultural significance further underscores the importance of understanding the historical presence of manatees in the Lesser Antilles. While existing records provide some understanding, there is still much to learn about the historical presence of manatees in the Lesser Antilles. Further research into the historical record---including museum archives, journals of explorers and residents---and zooarchaeological data has the potential to shed more light on this history.

Rare sightings in recent years, categorised with presence code of ‘extant,’ were documented in the following countries of the Lesser Antilles: Sint Maarten in 1987/1988 (Debrot et al. 2006); Curacao in 2001 and 2005 (Debrot et al. 2006); Virgin Gorda, British Virgin Islands in 2003 (Mignucci-Giannoni unpubl. data); Anegada and Tortola in the British Virgin Islands in 2022 (Mignucci-Giannoni unpubl. data); the Cayman Islands in 2006 (Dave Murphy pers. comm.); Turks and Caicos Island in 2014 (DEMA 2014); St. Croix, US Virgin Islands in May 2018 (The St. John Source 2018); Aruba in January 2018 (BioNews 2018); and Bonaire in 2018 (The Bonaire National Marine Park Information 2018). Manatees are considered to be ‘extinct’ (i.e., extirpated) in the other islands of the Lesser Antilles (see distribution codes in Country list).

Puerto Rico:
The general distribution of manatees in Puerto Rico has not changed in the last 40 years. Manatees can be found in all the estuaries and coastal waters extending over the insular shelf, from Dorado, clockwise around the island to Añasco, including Vieques Island, and recently off Culebra Island (Collazo et al. 2019). Recent sightings from Rincón to the town of Manatí, particularly in Aguadilla, have risen during the past decade. A single manatee report was recorded from Mona Island (N. Jiménez pers. comm. 2021). While manatees use river mouths for drinking fresh water, they seldom enter rivers, except for the Loíza, Loco, Bucaná, La Plata, and Guanajibo rivers (Mignucci-Giannoni et al. 2018, Caribbean Manataee Conservation Center unpubl. data, G. Rodríguez pers. comm. 2021). It seems that the narrow insular shelf of Maunabo on the southeast coast, and from Rincón to the town of Manatí on the northwest and north coasts, serve as geographical barriers for the two main genetic populations of the island (Hunter et al. 2012). Recent records suggest that manatees are more widespread, expanding their distribution and exploring previously unreported areas, such as some of the cays on the south coast (Mignucci-Giannoni et al. 2018).

FRESHWATER BODIES AND RIVERS: Many freshwater bodies along the distribution range from the USA to Brazil and in the Greater Antilles, including the rivers and lakes listed below.

MAJOR RIVERS:

• USA: St. Johns River, Suwannee River, Manatee River, Caloosahatchee River, St. Lucie River, and Crystal River – all in Florida.
• Mexico: Coatzacoalcos, Usumacinta, Grijalva, Palizada, Candelaria, Chumpan, and Hondo rivers.
• Belize: New, Belize, Sibun, Monkey, Deep, Sarston rivers, and Indian Hill Lagoon.
• Guatemala: Dulce, El Golfete, and Livingston-Motagua rivers.
• Honduras: Cuero y Salado, Chapagua, Aguán, and Platano rivers.
• Nicaragua: Wawa, San Juan, Prinzapolka, and Bambanain rivers.
• Costa Rica: Colorado, San Juan, Tortuguero, Sixaola, and Carbon rivers.
• Panama: San San, Negro, Manatí, and Caña rivers.
• Colombia: Atrato, Sinú, San Jorge, Cauca, Magdalena, Frío, Meta, Orinoco, Lebrija, Cesar rivers.
• Venezuela: Orinoco, San Juan, Boca del Dragón, Cinaruco, and Capanaparo rivers.
• Guyana: Most of coastal rivers in Guyana.
• Suriname: Saramacca, Suriname, Nanni, Coppename, Corantijin, and Nickerie rivers.
• French Guiana: Maroni, Mana, Iracoubo, Sinnamary, Kourou, Kaw, and Ouanary rivers.
• Brazil: Parnaiba, Ubatuba, Timonha, Camaratuba, Mamanguape, Miriri, Paraíba, Goiana, Cardoso, Tatuamunha, Vaza-Barris, Real-Piauí, Camurupim, Oiapoque, and Guajú rivers.
• Cuba: Hatiguanico, La Coloma, Almendares, Camaguey, Sagua, Agabama, and Cauto rivers.
• Puerto Rico: Loco River and Bucaná River.

MAJOR LAGOONS and ESTUARIES:

• USA: Indian River Lagoon, Lake Worth Lagoon, Tampa Bay, Charlotte Harbor – all in Florida.
• Mexico: Laguna de Alvarado, Laguna de Términos, Yalahau, Bahía de la Ascensión, Bahía Espíritu Santo, and Bahía de Chetumal.
• Belize: Southern Placentia, and Indian Hill.
• Guatemala: La Graciosa. Honduras: Caratasca, Thompson and Gauimoreto.
• Nicaragua: Bismuna, Wounta, Pahara, Krukira, Karata San Juan, and Gracias a Dios.
• Costa Rica: la Garza, Cahué, Dos Bocas del Colorado, and Gandoca.
• Panama: San San Pond Sak, Changuinola, Sorota, Bocas del Toro.
• Colombia: Ciénaga de Zapatosa, Ciénaga Grande de Santa Marta, and Ciénaga Grande de Lorica.
• Venezuela: Tablazo Bay.
• Brazil: Parnaíba, Timonha-Ubatuba, Mamanguape, Tatuamunha, Goiana, Real-Piauí.
• Cuba: Bahía Nipe-Banes-Levisa, Guantánamo, Santiago de Cuba, de Cochinos, Ciénega de Zapata, and Cortés.
• Puerto Rico: Jobos, San Juan, Condado, Torrecillas, Boca Vieja, Comezón, Honda, Boquerón, Guánaica, Tallaboa, and Guayanilla.

MAJOR LAKES:

• USA: Lake Okeechobee and Lake George, Florida.
• Mexico: Catazajá.
• Guatemala: Izabal.
• Panama: Gatun.
• Venezuela: Maracaibo.

Area of occupancy and extent of occurrence Here we discuss what is known about area of occupancy (AOO) and extent of occurrence (EOO) and why quantitative estimates are not provided for the species as a whole. 
AOO: The area of occupancy may be expressed as the smallest critical or “essential” area that is able to sustain the current population through some temporary time frame. For the Florida Manatee, this smallest “essential” area corresponds to the waters manatees occupy during the coldest days of the year, when they aggregate around natural and man-made warm-water sources (Laist et al. 2013). Estimates of AOO have ranged from 38 to 780 km², as discussed in the corresponding subspecies account (Deutsch and Valade in press), but estimation of this parameter needs further work to improve accuracy and match the IUCN-required 2 x 2 km scale (IUCN 2017). The distribution of various populations of Antillean (Greater Caribbean) Manatees contract seasonally during the dry season. In flood-pulse river systems, water levels drop and manatees move into deeper water bodies (e.g., lakes, lagoons) or downriver; along the coast, manatees living in areas with strong seasonality of precipitation may move closer to river mouths in order to access freshwater during the dry season (Favero et al. 2020, Deutsch et al. 2022a). There is no accurate information to estimate the temporal reduction of suitable habitat during dry conditions over the subspecies range. However, given the extensive range and large EOO for the West Indian Manatee overall, it does not seem possible that the AOO could fall below the threshold for Vulnerable of 2,000 km².

EOO: The extent of occurrence measures the spatial spread of a species’ distribution. As a migratory species in much of its range, the EOO is based on the smallest seasonal distribution for manatees (IUCN 2017), which is winter for the Florida Manatee and the dry season for many subpopulations of the Antillean (Greater Caribbean) Manatee (Deutsch et al. 2022a). As detailed in the T. manatus manatus subspecies account (Morales-Vela et al. in press), the range extends over a linear distance of approximately ~16,637 km of coastline from the state of Tamaulipas, Mexico, to the state of Alagoas in northeastern Brazil, including countries in the Greater Antilles. Using a swath of 2 km from the coast yields a coastal EOO of approximately 33,274 km². This distance band from shore is based on manatee locations obtained through aerial surveys (e.g., Morales-Vela et al. 2000, Alves et al. 2013, Collazo et al. 2019), movements of radio-tracked manatees (e.g., Castelblanco-Martínez et al. 2013, Normande et al. 2015, Morales-Vela and Bahena-Basave 2023), and manatee habitat characteristics (e.g., Olivera-Gómez and Mellink 2005). Morales-Vela et al. (in press) considered that the total EOO estimate may increase to approximately 118,842 km² if freshwater ecosystems (including rivers, lakes, lagoons, wetlands) and offshore habitats (e.g., keys, atolls) that are inhabited by manatees across the species’ range are included.

The EOO for the state of Florida was originally estimated to be ~19,500 km², based on waters within large bays, estuaries, and accessible rivers and lakes, plus remaining areas lying between the shoreline and the 12-foot depth contour for the entire state (Haubold et al. 2006). It was later determined that EOO should have been based on its winter range rather than its year-round distribution (IUCN 2017); the metric was not recalculated with updated information, however, because a review of the criteria indicated that it would not make a difference in Red List status under criterion B for the Florida Manatee (Deutsch and Valade in press). Likewise, despite lacking an accurate estimate, we know that total EOO for the West Indian Manatee is much higher than the 20,000 km² threshold required for the Vulnerable classification under criterion B1.

Population abundance is poorly known in most countries within the species' range and is still based on anecdotal information for several countries. Our best estimates and guesstimates, based on available data and opinions from in-country experts, are that the total worldwide population is approximately 17,120 animals (9,805 Florida Manatees, including 15 in The Bahamas that likely include manatees originating from both subspecies; 7,315 Antillean (Greater Caribbean) Manatees). The minimum number is estimated at 12,034 animals (8,365 Florida Manatees; 3,669 Antillean (Greater Caribbean) Manatees). Most of the West Indian Manatee population lives in the United States: 69.4% of the minimum and 57.2% of the best estimate of the species' total abundance. The proportions of mature individuals are estimated to be 0.57 and 0.73 for Antillean (Greater Caribbean) and Florida Manatees, respectively (see subspecies accounts for details). The number of mature individuals is estimated to be a minimum of 8,197 (6,106 Florida Manatees; 2,091 Antillean (Greater Caribbean) Manatees), with a best estimate of 11,328 mature individuals (7,158 Florida Manatees; 4,170 Antillean (Greater Caribbean) Manatees). See the Supplementary Material (Table S1) detailing estimates of abundance for the West Indian Manatee by country and subspecies; the country-specific estimates for Trichechus manatus manatus were taken from that subspecies' red list assessment prepared by Morales-Vela, Mignucci-Giannoni, and Quintana-Rizzo in 2024. Information on population status is provided below separately for each subspecies.

Current Population Trend for T. manatus: The ‘current population trend’ field is meant to convey a snapshot of the probable status of a population within the IUCN assessment cycle, but it is not part of the criteria used to determine the appropriate Red List category. The term “refers to trends over a period of ca. three years around the present” (IUCN 2013, p. 21). Clarification on the meaning and determination of current population trend was provided by IUCN staff: “the period under consideration should be six years: based on knowledge of population trend over the three years immediately before the assessment date and the projected trend over the next three years, is the population likely to be stable, declining, increasing, or is the current population trend unknown?” (C.M. Pollock pers. comm. to Benjamin Morales, 6 January 2022). In our case, the period under consideration is from August 2020 to August 2026. This trend is listed as unknown for the Florida Manatee (see 'Population Information' in the subspecies account for rationale) and decreasing for the Antillean (Greater Caribbean) Manatee. Given the lack of up-to-date information, and the need to combine trends for the two subspecies, assigning 'unknown' to this field was deemed the most appropriate answer.

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T. manatus latirostris (Florida Manatee)

There is a wealth of knowledge about the life history and population biology of the Florida Manatee, built upon long time series of data collected using photo-identification, satellite telemetry, aerial surveys, carcass salvage and necropsy, and genetic analyses. Manatees can live to at least 60 years of age, become sexually mature at about 4–7 years old, have a low reproductive rate (one calf every ~2.5–3 years), and a calf dependency period lasting ~1.5–2 years. This life-history strategy requires a high survival rate among adults for the species to persist.

Abundance: Since the time of the last Red List assessment (Deutsch et al. 2008), an innovative approach has been taken to estimate the abundance of Florida Manatees, along with a quantitative measure of uncertainty. Martin et al. (2015) integrated multiple sources of information from a stratified random sampling design, double-observer protocol, repeated passes around survey plots, and manatee dive data to account for spatial variation and imperfect detection of manatees. This approach has been further improved upon by Hostetler et al. (2018) and, most recently, by Gowan et al. (2023), whose state-wide estimate of abundance in 2021–2022 was 9,790 manatees (95% credible interval (CI): 8,350–11,730), of which 4,630 (3,960–5,420) were on the west coast of Florida and 5,160 (3,940–6,980) were on the east coast. Gowan et al. (2023) caution against inferring trends from the abundance data alone. Rather, these abundance estimates are most appropriately used in the context of the Integrated Population Model (see below), which incorporates multiple data sources to generate a more accurate assessment of population size and trends (Hostetler et al. 2021). The estimated proportion of the population that is mature (i.e., at least 4.5 years old) is 0.73 (Supplementary Data SD3 in Lonati et al. 2019), resulting in a point estimate of 7,147 mature individuals in the United States in 2021–2022 (6,096 for the lower 95% credible limit of abundance). Adding in a small number of manatees from the Bahamas (15 total, 11 mature) results in a total for the Florida subspecies as follows: best estimate of 9,805 total and 7,158 mature; and a minimum reasonable estimate of 8,365 total and 6,106 mature (see Supplementary Information Table S1). Thus, abundance for the subspecies meets the first part of criterion C (i.e., <10,000 mature individuals).

Additional information on manatee abundance in Florida comes from near-annual synoptic surveys conducted through 2019, which are timed to coincide with periods of very cold weather when most manatees aggregate at a limited number of warm-water sites in their winter range. The highest state-wide count obtained during these surveys was 6,620 manatees in 2017 (FWC 2018). This represents a minimum bound on abundance because the surveys were not designed to estimate detectability, so the fraction detected is unknown. The highest synoptic counts to date for the west and east coasts of Florida are 3,339 (Jan–Feb 2019) and 3,731 (Jan 2018), respectively (FWC 2021).

Subpopulations: For population assessment purposes, the Florida Manatee population has been divided into four geographic regions (Northwest, Southwest, Atlantic, and upper St. Johns River), sometimes referred to as subpopulations (USFWS 2001) or ‘management units’ (FWC 2007). Radio-tracking and photo-identification studies have shown that manatees within each region tend to use the same network of warm-water sites during winter and have similar, often overlapping, distribution patterns outside of winter (Bengtson 1981, Rathbun et al. 1990, Reid et al. 1991, Weigle et al. 2001, Deutsch et al. 2003b). These studies have also found that movement of individuals between east and west coasts is limited, but dispersal between regions within a coast is somewhat more frequent (FWC, USGS, and Mote Marine Laboratory, unpublished data). Regardless of whether the degree of genetic or demographic exchange warrants the subpopulation label, these regions differ in habitats, major threats, and (in some cases) vital rates; as such, it has proven useful to analyze population status and trends separately for the four regions.

The Northwest region (NW) extends from the Pasco-Hernando County line along the central Gulf coast northward through the Florida Panhandle and including the coastal areas of adjoining Gulf of Mexico states. The Southwest region (SW) extends from the Pasco-Hernando County line southward to Cape Sable in Monroe County. The Atlantic region (ATL) extends along the entire east coast of Florida (including the Florida Keys and Florida Bay), coastal states northward along the Atlantic seaboard, and the lower St. Johns River north of the Clay-Putnam County line. Manatees in the Upper St. Johns River region (USJ) live in a much smaller area in the river, lakes, and tributaries south (upstream) of the Clay-Putnam County line. The proportion of the population within each region was estimated from the 2011/2012 surveys by Runge et al. (2017) as follows: 10% in NW, 34% in SW, 51% in ATL, and 5% USJ. The relative proportions of manatees on the west and east coasts shifted in the 2015/2016 surveys (west 55%, east 45%), but the region-specific estimates were not considered comparable (in part due to a change in seasonal timing of surveys) (Hostetler et al. 2018).

Population Trends and Projections: Adult survival and female reproductive rates have been determined with high precision through application of state-of-the-art, mark-recapture analytical methods to sight-resight data acquired through photo-identification of distinctly marked individuals (Kendall et al. 2004; Langtimm et al. 2004, 2016). Mean annual adult survival rates, excluding additional mortality due to cold and red tide events, are high (0.97–0.98) in all four regions (Runge et al. 2017). Given the sensitivity of manatee population growth rate to adult survival (Eberhardt and O’Shea 1995, Runge et al. 2004), this has allowed the population to grow, and it provides resilience in the face of current and future threats. Population growth is reflected in increasing counts of manatees at a number of primary warm-water sites (e.g., Kleen and Breland 2014, Reynolds and Scolardi 2016).

Population Viability Analysis (PVA): A custom stage-based PVA model, termed the manatee Core Biological Model (CBM), was used to address the three IUCN criteria (A, C, E) that included metrics on the probability of future population decline or extinction. The CBM projected the population dynamics of manatees in each of the four regions independently (i.e., four separate models), based on region-specific estimates of vital rates and life history (Runge et al. 2017). The last year in which vital rates were estimated for the CBM varied across regions from 2009–2012 for adult survival and from 2010–2014 for reproductive rate. The CBM incorporated demographic and environmental stochasticity, as well as uncertainty in parameter estimates and, in some cases, uncertainty in model structure. The ‘baseline’ scenario included plausible future threats to manatees and their habitat, including expected declines in carrying capacity through loss of warm-water habitat (i.e., loss of power plant thermal discharges, declines in spring flow), increases in cold mortality as warm-water habitat declines and carrying capacity is approached, and increases in the frequency of unusual mortality events due to red tide.

With respect to criterion A, the probability of the adult manatee population in Florida (i.e., essentially, the subspecies) declining by at least 30% over three generations (taken to be 60 years, Haubold et al. 2006) was calculated to be 0.3% under the CBM ‘baseline’ scenario (Runge et al. 2017). The probability that such a decline would occur on either the east or the west coast of Florida was estimated to be 6.6%. Regarding criterion C, the probability of the adult manatee population in Florida declining by at least 10% over 60 years was estimated to be 1.5% under the CBM ‘baseline’ scenario (Runge et al. 2017). The probability that such a decline would occur on either coast of Florida was an order of magnitude higher at 15.5%. The metric in criterion E is the probability of extinction in the wild in 100 years. Runge and colleagues (2017) preferred a quasi-extinction metric for several reasons, including that population dynamics become challenging to forecast and unpredictable at extremely low population sizes. They calculated that the probability of the adult manatee population falling below a quasi-extinction threshold of 500 animals (i.e., an effective population size of 250 adults, based on Tucker et al. (2012)) on either coast of Florida over 100 years is only 0.4% under the ‘baseline’ scenario. It was higher under two other scenarios considered: 6.0% under a scenario of multiple emerging threats; and 8.2% under a hypothesis of density-dependent mortality underlying two cold-related unusual mortality events. These probabilities would be lower if applied at the state-wide (subspecific) scale.

As a consequence of expected losses of industrial warm-water habitat, the CBM forecasts major shifts in the population distribution among regions—from the two southern regions, where most manatees currently rely on power plant thermal discharges for warmth (Laist et al. 2013), to the two northern regions, where manatees use artesian spring systems (Runge et al. 2017). Odds are nearly 50:50 that the SW and ATL subpopulations (where most manatees currently reside) will decline by 30% or more over the coming century. Runge et al. (2017) noted that: “… the relatively low probabilities of quasi-extinction at the [state-wide and] coastal scale mask higher risks of decline at the regional level” (p. 37). They concluded that “… the risk of major population decline is very low at the state-wide (subspecies) level, moderate at the coastal level, and high at the regional level for the two currently largest management units. This seeming paradox stems from the fact that one regional population is expected to decline and one to increase on each coast” (p. 34). Finally, additional scenarios were run to explore sensitivity of population metrics (particularly quasi-extinction) to various parameters and to evaluate the impacts of potential emerging threats. The scenario in which multiple emerging threats co-occur would have the greatest impact on the population. Relative to the baseline scenario, this scenario added: (a) a 50% increase in the watercraft-related mortality rate, (b) immediate loss of warm-water carrying capacity associated with coal-fired power plants, (c) long-term 50% reduction of carrying capacity at natural springs (vs. 26% reduction for mean baseline), (d) increased frequency of cold winters, and (e) a 2% reduction in survival in the ATL region due to a chronic source of mortality. Under this scenario, the probability of quasi-extinction (500 adult threshold) on either coast over 100 years was estimated to be 6.0% (Runge et al. 2017).

Integrated Population Model (IPM): Hostetler et al. (2021) built an IPM that reconstructed historical population dynamics for manatees in the SW region of Florida from 1997–2016. This IPM integrated multiple sources of population data, including two estimates of abundance from aerial surveys (Hostetler et al. 2018), number of verified carcasses by size/age class, and estimates of adult survival and female reproductive rates from sight-resight analyses based on photo-identification. The population in the SW region was estimated to have increased at an average rate of 2% (95% CRI, 1–3%) per year over this 19-year period, from 2,014 manatees (95% CRI, 1,861–2,229) in 1997 to 2,966 manatees (95% CRI, 2,551–3,434) in 2016 (Hostetler et al. 2021). The model generated estimates of parameters that had been missing, such as survival of calves and subadults, and population size in years before and between abundance surveys. They found that an intense red tide bloom in 2013 caused an 11% decline (95% CRI, 7–15%) in the regional population, with particular impacts on calf and subadult mortality. This modelling approach provided estimates of population parameters that were more accurate or more precise (or both) than existing estimates. For example, the baseline survival probabilities for calves and subadults in the CBM were derived from a small, old study in the USJ region and extrapolated based on ratios to adult survival probability (Runge et al. 2017). For the SW region, survival rates of immature classes (first 4 years) estimated from the IPM were substantially lower than the extrapolated estimates used in the CBM. The IPM approach to evaluating current and past population dynamics and status will be extended to the other three regions and also applied at coastal scales.

Unusual Mortality Event (UME) in the Atlantic Coast Region: Starting in early December 2020, an unprecedented number of manatees died in the Atlantic coast region of Florida during the winter and spring of 2020–2021, and a high level of mortality occurred again in the subsequent winter (Deutsch et al. 2021, FWC 2023a,b). The number of carcasses documented in the Atlantic region during the months of December through March of 2020–21 (582) and 2021–22 (457) was 5.0 and 3.9 times higher, respectively, than the prior five-year average for those months (116.4, December 2015 – November 2020). Over the course of these two winters, 59% of carcasses from the Atlantic region were found in the waters of Brevard County (northern IRL); the number of carcasses and live manatees in distress were substantially elevated in southeast Florida during the first winter as well. The state-wide number of verified manatee carcasses hit a record-setting 1,100 in 2021, nearly double the recent five-year average of 579 (calendar years of 2015–2019); 800 carcasses were documented in 2022 (https://myfwc.com/research/manatee/rescue-mortality-response/statistics/mortality/).

The investigation into this UME is ongoing, but it is clear that the primary cause of mortality was starvation. Poor body condition of malnourished animals also made them more vulnerable to the stress of cold winter temperatures. Externally, emaciation presented as a distinct dip between the head and the rest of the body (“peanut head”), longitudinal ventral folds, flattening of the body, appearance of an elongated peduncle area, and sometimes visible outline of skeletal structures such as the skull. Necropsied carcasses had findings of significant emaciation and profound atrophy of fat, muscle, and other internal organs, especially liver (FWC 2023b). Often there was little or no filling of the gastrointestinal tract. Health impacts of chronic malnutrition appear to be long-lasting, showing up in the warm season as well (FWC 2023b). There is preliminary evidence suggesting a large decline in reproduction during the UME. Manatees were malnourished and starving due to the massive loss of seagrass in the IRL that had been steadily worsening since 2011 due to repeated algal (phytoplankton) blooms (Morris et al. 2018, 2022); SAV has been declining in other areas along the east coast as well (see Threats to Manatee Forage Habitat under Threats section below).

The impact of this crash in environmental carrying capacity on manatee population dynamics has not yet been determined, but preliminary indications are that it is likely to be large. Carcass counts in the Atlantic region during winter 2022–23 were at or below baseline levels, apparently because manatees were in better body condition than the prior two winters. Recovery of seagrass in the IRL will be vital to improvement in manatee health and survival. Updates on the UME are posted by the Florida Fish and Wildlife Conservation Commission here:https://myfwc.com/research/manatee/rescue-mortality-response/ume/.

Population Genetics: Genetic diversity within a population can affect the organism’s ability to adapt to long-term environmental change. In this regard, the Florida Manatee may have limited capacity for adaptation through genetic evolutionary change, as it has very low genetic diversity. This is borne out through analyses of mitochondrial DNA (only one haplotype) and nuclear DNA (relatively low levels of polymorphism and allelic diversity in microsatellites) (Garcia-Rodriguez et al. 1998, Vianna et al. 2006, Tucker et al. 2012). Either a founder effect or a population bottleneck, or both, could account for the current situation. Tucker et al. (2012) found little genetic differentiation among regions or coasts.

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T. manatus manatus (Antillean Manatee or Greater Caribbean Manatee)

Based on the best available published and unpublished scientific information and in conjunction with the advice of national experts and the members of the Sirenia Specialist Group, the minimum population estimate of the Antillean (Greater Caribbean) Manatee is 3,669 individuals, with the best estimate of 7,315 manatees (Supplementary Information Table S1). Information gaps have constrained the ability to produce a reliable population estimate for several countries and the entire range of the species. This restriction has been exacerbated by the difficulties of counting manatees in dark turbid waters, often covered with dense vegetation. Besides, the manatees show an elusive behaviour that makes observing in the wild extremely difficult. Different survey techniques have been attempted, sometimes within the same country. No new information has been generated in many areas of the species range since the last Red List assessment in 2008. In several countries, it is unknown whether the populations are still present or have disappeared. Thus, there is significant uncertainty around this regional population estimate for this species; however, it is the best available information so far and a feasible robust estimation under these restricted conditions.

Mature individuals are a significant demographic group due to their reproductive effects on the species' survival. Not only does the number of mature individuals have consequences for reproduction, but also the quality or fitness of these individuals is essential, which is beginning to be investigated in sirenians (Marsh et al. 2011, p. 340). Another aspect to consider is that several manatee populations are still under hunting pressure that has not been evaluated (see section on Threats). Based on the great uncertainty in estimates of population size (Supplementary Information Table S1), we consider it appropriate to apply the average (57%) of upper (70%) and lower limits (45%) of the percentage of mature individuals based on various populations of sirenians (Marsh et al. 2011, p. 339). Thus, for the crude minimum population size of 3,669, the number of mature individuals would be 2091 (Supplementary Information Table S1). Adopting the precautionary approach to select the more protective category, the estimated number of mature individuals meets the first condition of Criterion C for Endangered species of <2,500 mature individuals.

Given the threats facing manatee populations throughout much of their range, it is considered that the Antillean (Greater Caribbean) subspecies could decline by at least 20% over the next two generations. Assuming a generation time like that of the Florida Manatee, estimated to be 20 years (Haubold et al. 2006, Deutsch et al. 2008, Marsh et al. 2011), this represents a population reduction in 40 years. It is important to highlight that, unlike the Florida Manatee, some subpopulations in central and South America still suffer exploitation despite legal protections. Thus, the reduction of its population could occur in a shorter time. This population change meets the following condition of criterion C: an estimated continuing decline of at least 20% within five years or two generations, whichever is longer.

A PVA conducted by Castelblanco-Martínez et al. (2012) described the Antillean (Greater Caribbean) Manatee with an estimated total population size of 6,700 manatees structured as a metapopulation with an arbitrary migration rate among regions of 1–2%. Lacking data on survival and reproductive rates, as well as other demographic parameters, values for vital rates used in the analyses were approximated from information on the Florida Manatee, as well as an unpublished study from Costa Rica. The baseline model assumed anthropogenic mortality of only 1% and the result was positive population growth. This result conflicts with anecdotal observations of apparently declining populations in many countries. Growth rate and probability of quasi-extinction were very sensitive to changes in assumptions about the level of natural and human-caused mortality, as expected for a long-lived mammal with a low reproductive rate. Given the severe data limitations, we consider the results of this paper as being potentially helpful in evaluating the sensitivity of manatee population dynamics to various factors (although parametric uncertainty was not sufficiently accounted for), but the findings could be potentially misleading as an estimate of current population growth or a projection of future population viability.

Manatee populations have only been confirmed in 19 of the 42 countries where the subspecies have been reported through historical records (Supplementary Information Table S1). In at least ten countries, available data continues to be mainly based on anecdotal information and expert opinion rather than on systematic surveys and quantitative evidence. Countries with adequate and extensive habitat for manatees, such as Colombia and Venezuela, lack recent or any population estimates. In other countries, the existing data is limited and fragmented. Yet, countries such as Belize, Brazil, Dominican Republic, French Guiana, Guatemala, Honduras, Mexico, Panamá, and Puerto Rico have made relevant research efforts to estimate the size of their populations. In the case of Mexico, new technological resources (sonar and telemetry), combined with field studies, have helped to estimate new data on the abundance of the species in dark, turbid waters. These new data support a less optimistic scenario (e.g., Puc-Carrasco et al. 2017) than the previous one reported in the 2008 Red List assessment (Deutsch et al. 2008).

Early evidence of a large-scale decline of Antillean (Greater Caribbean) Manatee populations throughout much of its range was documented by Lefebvre et al. (2001). At that time, the subspecies was reported as severely reduced, rare, or absent in many areas where they had been previously present and existed in high numbers (Husar 1978, O'Shea et al. 1988, Morales-Vela et al. 2003, Serrano et al. 2007, Normande et al. 2015). Unfortunately, this condition has probably not changed, and the consensus of experts is that the different subpopulations are declining in most countries (Supplementary Information Table S1).

Except for Puerto Rico (Mignucci-Giannoni et al. 2018, Collazo et al. 2019), there is no evidence that manatee numbers have increased from Mexico to Brazil, including the Greater Antilles. In the case of Haiti, its local manatee population is at critical risk of extinction in the next few years (Mignucci-Giannoni and Aquino 2020). The situation in Haiti affects the manatee population in the neighbouring country of the Dominican Republic, both on the island of Hispaniola, which still has some unregulated threats to manatees, and where the manatee population is perceived to be declining (Dominguez-Tejo 2019). Cuba has registered a large percentage of annual manatee deaths. At least 86 manatee carcasses were identified between 2001 and 2018. This is an average mortality of 4.6 manatees per year (not including unreported carcasses), in which 77% (n = 63) of mature manatees died (Alvarez-Alemán 2019). In Colombia, between 2006 and 2007, in the Atrato River, at least one manatee was killed each weekend for meat consumption (D. Caicedo pers. comm. 2018).

In countries with significant manatee presence, such as Belize, Brazil, Colombia, and Mexico (see Supplementary Information Table S1), several threats can put those populations in a fragile situation, and changes in those populations could have an effect at a regional level. For example, Brazil contains a significant proportion of this subspecies within its borders (see Supplementary Information Table S1). In 2019, the most extensive oil spill in the country's history occurred on the northern coastline in the state of Maranhao, considered one of the last major strongholds for manatees (Siciliano et al. 2020). According to the Brazilian Environment Institute (http://www.ibama.gov.br/manchasdeoleo-localidades-atingidas), at least 17 tons of crude oil were removed during clean-up efforts, but much of the oil remains in the area. Manatees and their related habitats were believed to be significantly impacted by the oil spill (Magris and Giarrizzo 2020).

Another example includes the populations of the Mexico, Belize, and Guatemala regions. These populations represent about 31% of the global Antillean (Greater Caribbean) Manatee population (see Supplementary Information Table S1). Two countries (Mexico and Belize) have experienced significant mortality events in recent years, and their effects on the region's population are unknown. Since manatees can move between the neighbouring countries of Mexico and Belize (Morales-Vela et al. 2007, Castelblanco-Martinez et al. 2013) and Guatemala, a decrease in the local manatee populations could have severe regional effects.

In the case of Mexico, an unusual mass mortality event of 48 manatees occurred in a freshwater ecosystem in the southern Gulf of Mexico in 2018 (Morales-Vela et al. 2018). This mortality event represented a loss of 8.4 to 9.6% of the estimated manatee population in the state of Tabasco, which is thought to have the largest manatee population in Mexico (D. Olivera and B. Morales-Vela pers. comm. 2019). The specific causes of this mortality event are still unidentified. The event was associated with a combination of limited water movement (eutrophication), high temperatures, high prevalence of faecal coliforms in the water of the river, and harmful algal blooms of cyanobacteria (Morales-Vela et al. 2018). Harmful algal blooms are becoming increasingly common in freshwater ecosystems globally (Ho and Michalak, 2015). It is a new concern for countries with large numbers of manatees in freshwater ecosystems, as in most of this subspecies' distribution (Reynolds III and Odell 1991).

Belize was considered the last stronghold for manatees in the Caribbean Sea (O´Shea and Salisbury 1991). In the 1995–2020 period, the country experienced alarmingly high mortality, with annual average mortality of 17 manatees, with approximately seven events related to anthropogenic causes, one of them being watercraft collision (Galves et al. 2022). These authors also indicate that the average mortality rate exceeded the national Potential Biological Removal (PBR) in several years. Since 2010, manatee stranding has increased, with an average stranding rate of 13.9 per year. This increase appears to be positively associated with the rapid growth of the tourist industry, with more cruises and boating activities within habitat areas of high manatee concentrations (Barrera-Mora 2018, Galves et al. 2023). Galves et al. (2022) report that the highest number of manatee standings during 23 years of monitoring occurred in 2018, a year in which tourism increased by 17% or nearly 1.4 million visitors (Belize Tourism Board 2018). Watercraft mortality is growing and is one of the main threats to manatees in Belize (Ortega-Argueta et al. in prep.; Galves et al. 2022, 2023). The increased boat traffic in priority areas for manatees (manatee hotspots) in Belize raises concerns about the survival of the largest manatee population in the Caribbean region (Galves et al. 2023), with regional implications for the neighbouring manatee subpopulations of Mexico and Guatemala. The presence of manatees with non-lethal scars by boat propellers on the southern coast of Quintana Roo and Chetumal Bay, on the Belize border, has increased recently. In 2021, of nine manatees captured for medical evaluation in Chetumal Bay, three had scars or mutilations on their tails. In 2022, on the southern coast of Quintana Roo, of 105 manatees that were photo-identified, 13 (12.4%) had cuts caused by propellers (Morales-Vela and Bahena Basave 2023).

Guatemala has a manatee population estimated to be around 150 individuals. This is a small population compared to the manatee populations of Mexico and Belize. The estimated potential biological removal rate (PBR) for this population of 150 manatees was 0.6, or equivalent to one manatee. This PBR was exceeded in each reported mortality year between 1992 and 2022 (Machuca-Coronado et al. 2023). Notably, there is a significant lack of knowledge of the population, especially given the focus on manatee strandings (Corona-Figueroa and Cifuentes-Espinosa 2024).

The manatee population has been studied in Puerto Rico since 1976 through radio-telemetry, population health assessments, aerial surveys, and stranding response. Over the years, an increase in their mortality has been observed, with a total of 296 carcasses recorded between 1980–2021. In the 1980s, the average number of manatee deaths per year was 3.7. Most undetermined causes of death resulted from the advanced state of decomposition of bodies, followed by watercraft collisions and orphaned calves. By the 1990s, the average mortality increased to 6.2 manatees per year, mainly due to orphaned calves, watercraft collisions, undetermined and illness, respectively (Mignucci-Giannoni et al. 2000). The number of deaths per year has continued to rise in the 2000s decade with an average of 8.3 manatees per year and in the 2010s with 9.8 manatees per year (Bonde et al. 2012; C.I. Rivera Pérez pers. comm. 2021). The mortality rate is 10.6 manatees per year, with 50% due to watercraft collisions and 31.3% due to illness. These numbers show that the mortality of manatees in Puerto Rico has been increasing considerably during the past four decades, particularly post-COVID pandemic, and this is alarming for such a small population compared to other countries.


In this section, manatee population estimates are provided by country:

Belize:
Belize supports one of the largest populations of manatees in the Caribbean region. In 2012, the highest count ever recorded was 507 manatees, with 10% being calves (N. Auil-Gomez, unpublished data; Edwards et al. 2014). The estimated population size of manatees is probably closer to1000 individuals (Edwards et al. 2014; N. Auil-Gomez pers. comm. 2018; Bob Bonde pers. comm.).

Local genetic studies have not detected signs of decreased fitness by inbreeding depression that could increase the risk of extinction (Hunter et al. 2010). However, any reduction in the population could increase the inbreeding threshold, affect its fitness, and increase the population's risk of extinction. From 2008 to 2018, the increasing mortality of manatees has resulted in a total of 289 deaths, with watercraft collisions as the leading cause (Auil and Valentina 2004 cited in UNEP 2010, Castelblanco et al. 2019, Galves et al. 2022).

Genetic differentiation, presence of private alleles, and discrepancy in the haplotype proportions indicate restricted admixture between local populations associated with female philopatry and male-biased gene flow (Hunter et al. 2010). Regular long-distance movements of manatees between Mexico and Belize have been documented (Morales-Vela et al. 2007, Castelblanco-Martinez et al. 2013, Morales-Vela and Bahena Basave 2023).

Brazil:
Twenty years ago, the population was estimated to be around 500 manatees, based on interviews with local communities (Lima et al. 1997, Luna 2001). In 2010, aerial surveys were conducted to estimate the abundance and recorded 67 manatees in 55 sightings along 2,590 km of the coastline (Alves et al. 2015). By Bayesian analysis, these authors estimated a mean of 1104 manatees, with a confidence interval of 485 to 2221 and a high level of uncertainty. This updated Red List Assessment considers the low-range estimate of 485 as the minimum population size for West Indian Manatees in Brazil and the mean of 1104 as the closest possible population estimate (see Supplementary Information Table S1). There is no evidence of a population increase since the 1990s (Alves et al. 2015). On the contrary, a high extinction risk scenario is predicted if human impacts on the coastal zone continue increasing (Meirelles et al. 2022).

Colombia:
The Omacha Foundation estimated a minimum population of 500 manatees and 900 individuals as the closest population based on their long-term field efforts in various watersheds and rivers. Both estimates are based on interviews, manatee sightings, and rescued animals. The population estimation should be taken cautiously because no specific efforts have been made to quantify local populations. Manatee habitats are challenging to access and study in Colombia. Other national experts share this concern and acknowledge that knowledge about the local manatee population is still developing (Aguilar et al. 2015; K. Arévalo-González pers. comm. 2018).

Costa Rica:
There are no recent estimates of manatee abundance in the country. Reports of manatee sightings from the 1990s covered an extended area of rivers, lagoons, and artesian waters, “blue holes” along the Caribbean coast (UNEP 2010). Current reports indicate that more manatees occur in the coastal areas in the north zone on the border with Nicaragua and the southern border with Panama (C. Espinoza pers. comm. 2018). New sightings along the coast could be related to an increase in the abundance of the local population and a consequence of many years of protection and conservation actions conducted by the Fundación Manatí-Trichechus (C. Espinoza pers. comm. 2018). Based on all this information and the new reports of manatees on the coasts, it is estimated that the minimum population estimate is 100 manatees, and 250 is the possible manatee population.

Cuba:
The status of manatees remains ambiguous because field research has been limited, and the information is not well documented (Alvarez-Alemán 2018; 2021). However, the contemporary (past 2–3 generations) effective population size (Ne) can be estimated from existing microsatellite genotype data. The Ne estimate for Cuba is 50.5 (95% confidence interval: 25.8–63.7) (Alvarez-Aleman et al. 2022). The confidence interval suggests that these estimates are robust; however, it is essential to note that this estimate is of the recent past population, not the current population. Relating Ne to population size (N) can be calculated by assuming a Ne/N ratio between 0.1–0.5. Using the conservative ratio of 0.5, the minimum population size for Cuba is 100 individuals, and this population may only be as large as 238 individuals (A. Alvarez-Aleman and J. Austin pers. comm. 2020). Important caveats for these estimates are the sample size and distribution.

Dominican Republic:
The number of manatees inhabiting the coastal waters and rivers is not known. The minimum population is estimated to be 45 manatees, and the overall population estimation is 200 individuals (Supplementary Information Table S1), based on information provided by Dominguez-Tejo (2016, 2019). The country needs to prioritise research to implement a countrywide survey to obtain a better estimate of manatee abundance. Severe annual mortality continues on the island and must be urgently assessed and controlled (Dominguez-Tejo 2019). The manatee population in Hispaniola Island (Dominican Republic and Haiti) is considered declining (Dominguez-Tejo 2019).

French Guiana:
A minimum abundance estimate of 20 manatees was determined from nine surveys (aerial, boat, and interviews) (Castelblanco et al. 2017). The same study suggests that the manatee population could be more abundant given the extent of suitable habitat areas and that manatee encounters were relatively common compared to other manatee ranges. With this new information, it is accepted to consider a population of close to 150 manatees.

Guatemala:
In 2015, a workshop with local wildlife experts led to an update of the manatee population estimate for Guatemala from a minimum of 45 manatees (Quintana-Rizzo 1993) to up to 150 manatees (E. Quintana pers. comm. 2018). A cumulative total of 293 sightings and 518 manatees was observed during aerial surveys conducted from 1992 to 2022, including 476 adults (92%) and 42 calves (8%). Most manatee and calf sightings occurred inside protected areas where several priority areas were identified. Of these, the two priority areas were Refugio de Vida Silvestre Bocas del Polochic and Refugio de Vida Silvestre Punta de Manabique, which were identified as important manatee habitats in 1992 (Quintana-Rizzo 1993). No significant differences in manatee abundance were found over years, but significant differences in abundance were detected among survey sections and protected areas. Manatee numbers had positive significant correlations with ecological and human-related covariates. In addition, a shift in manatee distribution was recorded in 2014, although the cause is unclear (Quintana-Rizzo et al. 2023). In terms of mortality events, 43 recorded manatee stranding incidents involving a total of 48 manatees were recorded between 1992 and 2022. Of these, 96% (N = 46) were carcasses and only two were live animals. The age class distribution among the stranded manatees was determined for 46 individuals, with 61% classified as adults (n = 28), 26% as calves (N = 12), and 13% as juveniles (N = 6). The primary cause of mortality was attributed to poaching (70%, N = 21), followed by entanglement in fishing gear, also known as bycatch, which comprised 17% (N = 5) of incidents, with boat collisions contributing to 13% (N =4) of the total occurrences (Machuca-Coronado et al. 2023).

Guyana:
The local manatee's status is unknown. In 1963, Bertram and Bertram concluded that manatees were less frequent and abundant than in the distant past. In the late 1950s, approximately 80 adult manatees were introduced into dams and their canals to control the overgrowth of aquatic weeds. This experiment failed as manatee numbers gradually declined due to poaching and collision with the sugar cane-carrying barges (Haigh 1991). During an expert visit to the Georgetown Botanical Garden in 2014, at least 30 manatees were counted in ponds in the park (N. Castelblanco pers. comm. 2014). Additionally, during a visit to Guyana to rescue a manatee in 2015, over a dozen manatees were observed in the National Park (Botanical Garden), and over a dozen manatees were observed in the Guyana Zoo (C.I. Rivera-Pérez pers. comm. 2015). Based on this information and taking a precautionary approach, a minimum population of 50 manatees and a population of 100 manatees are estimated. The latter is supported by data from the UNEP (2010) and Self-Sullivan and Mignucci-Gianonni (2012). It is recommended that the country prioritises research and conducts nationwide surveys to obtain a more reliable estimate of the abundance of manatees. It is also recommended that the 30-plus manatees held at the Georgetown Botanical Garden be rehabilitated and released back into the wild to restore the wild stocks of the species in the country.

Haiti:
The local status of manatees is unknown. In 1982, a survey detected eight manatees (UNEP 2010). More recently, between 2019 and 2021, 11 manatees have been reported, of which eight have been killed (Mignucci-Giannoni and Aquino 2019; J. Aquino pers. comm. 2021). The eight animals were butchered, and their meat was sold for food. It is thought that the local manatee population is close to extinction. International collaboration is urgent, as well as strengthening national strategies for effectively conserving manatees and critical habitats to avoid their loss in Haiti. Binational cooperation between Haiti and the Dominican Republic should be strengthened to mitigate its effects on the Hispaniola manatee population.

Honduras:
In 2006, 11 manatees were sighted during six aerial surveys conducted on the north coast (González-Socoloske et al. 2011). Ten years later, wildlife rangers suggested that the manatee population could be between 60 to 80 manatees in the Refugio de Vida Silvestre Barras de Cuero y Salado and Parque Nacional of Cuyamel – Omoa. In a 2015 manatee workshop in Guatemala City, the Honduran wildlife rangers reported a detection rate of 0.37 and 0.58 manatees/hour at each refuge using side-scan sonar. Based on this new information, the minimum population could be 70 manatees, and a realistic population could be close to 250 manatees based on expert opinion (D. González pers. comm. 2023).

Jamaica:
The National Environment and Planning Agency (NEPA) Report of 2013 suggested that manatees in Jamaica are close to extinction. However, recent records indicated that there may be hope for the Jamaican manatee population. Although no current monitoring efforts have been carried out to assess the manatee population, there could be between 7 and 20 manatees, based on recent sightings. The most recent information was integrated by Damany Calder from NEPA in December 2020 and included one manatee sighted in Turtle Harbour, Portland, on December 6, 2020 (D. Henry pers. comm. 2020). Other manatee sightings occurred recently: one in Oyster Bay, Portland, in 2019 and one on 18 September 2020, near Alligator Hole, Manchester. Rangers from the Caribbean Coastal Area Management Foundation reported frequent sightings of manatees in 2016 within the Special Fishery Conservation Area, one near Falmouth, Trelawny, and three in Canoe Valley Wetlands (C. Barrett pers. comm. 2020). Additionally, conservation actions have been implemented as new Marine Parks and several Special Fishery Conservation Areas across the island have been developed (D. Calder pers. comm. 2020).

Mexico:
Genetic studies identified two manatee subpopulations, one in the riverine system and coast of the Gulf of Mexico, and another one on the Caribbean coast, eastern Yucatán Peninsula, with a limited or unidirectional gene flow from the Gulf of Mexico to the Caribbean Sea. Both subpopulations have low genetic diversity (Nourisson et al. 2011).

The population is estimated to be between 800 and 1,100 manatees (D. Olivera and B. Morales pers. comm. 2018), with approximately 300 individuals on the Caribbean coast (Morales-Vela and Bahena-Basave 2023). The largest subpopulation is thought to be between 600 to 850 manatees that are concentrated in the lower basins of the Grijalva and Usumacinta rivers in the states of Tabaco, Chiapas, Campeche, and Veracruz. There is no scientific information on population trends; however, according to the opinion of national experts, the population may be stable.

Nicaragua:
There is no recent information on the abundance of manatees in Nicaragua. González-Socoloske et al. (2011) observed 71 manatees during 18 hours of aerial surveys of the Miskito Coast. The coast of Nicaragua comprises one of the most extensive manatee habitats in Central America (Lefebvre et al. 2001). Jimenez (2002) estimated that Nicaragua has one of the largest manatee populations in the Caribbean Sea. Manatees travel more than 60 km from the coast up the rivers. Considering the recent conservation actions focused on manatees, it is estimated that the local population is 350 (D. González pers. comm. 2023).

Panama:
Manatees are distributed in several small areas along the Caribbean coast of Panama, with the two largest populations in Bocas del Toro and Lake Gatun in the Panama Canal (Muschett and Morales, 2020). The combined population estimate of these two areas is 110 manatees. Individually, Lake Gatun is estimated to have approximately 30 manatees (Muschett and Morales 2020), while Bocas del Toro is estimated to have 78–81 manatees (Merchan et al. 2019). Bocas del Toro includes two major areas: The Changuinola River and the San San Pond Sak Wetland (HSSPS), which includes the San San and the Negro Rivers. In the case of HSSPS, the estimated annual population ranges from 22–71 individuals (Guzmán and Condit 2017). In the case of the Changuinola River, the local estimate varies between 45 and 48 manatees (Díaz-Ferguson et al. 2017).

Lake Gatun is a small lake off the Panama Canal. The presence of manatees suggests that some individuals found a path to this location and could represent an isolated small subpopulation (Muschett and Morales 2020). It is unknown how many manatees represent the original subpopulation of this site and the effect of the Amazonian manatee introduced in 1964 on the genetics of the Panama manatee population.

Puerto Rico:
Recent aerial surveys conducted between 2010 and 2014 to estimate an island-wide abundance reported an average minimum population of 386 ± 89 manatees (Collazo et al. 2019). Based on this information, using the mean value of 386 manatees as the minimum population is considered appropriate. For the island-wide manatee population and taking a precautionary approach, there is an estimation of 618 manatees, which is the upper confidence interval from minimum island-wide assessments that include manatee hotspot and non-hotspot zones (see Supplementary Information Table S1; Collazo et al. 2019). This estimate is slightly lower than the 700 manatees suggested by the Caribbean Manatee Conservation Center (A. Mignucci-Giannoni pers. comm. 2018).

Suriname:
There is no recent information on the abundance of manatees. Duplaix and Reicher (1978 cited in Pool 2013) estimated a population between 500–600 manatees. In 1997, Wassink (cited in Pool 2013) estimated 200–300 manatees. Duplaix et al. (2001, cited in Meirelles et al. 2018) indicated that manatees were hunted to near extinction; however, they are still present in the country's northwestern region. Self-Sullivan and Mignucci-Giannoni (2012) estimated a population of 100 manatees. Pool (2013) considered this estimate too low and proposed that approximately 570 manatees inhabit the country. However, she recognises the lack of reliable information to estimate a local population. Therefore, taking a precautionary approach, we use the estimate of 300 manatees obtained by the Suriname Division of Nature Conservation as the current manatee population in the country.

Trinidad and Tobago:
There is no recent information on the abundance of manatees. Population estimates are based on surveys conducted in 1997 in the Nariva Swamp with at least 18 manatees (Romero et al. 2000). Manatees have also been reported in the Otorire River. Manatees, including young individuals, were confirmed in Mitan, Ortoire, Lebranche, and Salybia rivers in 2012 (Newsday, January 30, 2012). The presence of young individuals suggests relatively recent reproductive events in a population of a few manatees. Based on this new information, it is possible to think of a population of nearly 50 individuals.

Venezuela:
The current situation of manatees in Venezuela is unknown. The Venezuela Action Plan for Aquatic Mammals 2017–2027 does not include a manatee population estimate (Ferrer et al. 2017). National experts believe that the minimum population is approximately 250 manatees and that at least 100 live in the Lago de Maracaibo (A. Manzanilla; S. Boer, Y. Briseño pers. comm. 2020). A mating herd of six manatees in this lake was observed recently (Maricris Cordero pers. comm. 2022). Manatees are also believed to be present in several places along the Orinoco River, the Paria Peninsula, and other localities associated with hydrological systems (Ferrer et al. 2017), where their minimum population size could be 130–150 individuals. The Action Plan for Aquatic Mammals of Venezuela considers that in the last 50 years, the population has been declining, and that over the previous 10 years, more than 80% of the population has disappeared, and that reduced and dispersed populations still exist. Although the manatee is considered a critically endangered species with solid national legal regulations, hunting continues in different areas of Venezuela, affecting these unknown manatee populations. In December 2020, reports of illegal hunting and local trade in the locality of Yaguaraparo were confirmed by the authorities of the National Park of Turuéparo. Considering this and other threats and taking a precautionary approach, we apply a factor of 1.5 to the minimum population to estimate a current national population of 375 manatees. This estimate will be improved with future reliable information. (see Supplementary Information Table S1).

Information on habitats and ecology is provided below separately for each subspecies.

Trichechus manatus latirostris (Florida Manatee)

Much has been learned about the ecology, behaviour, and habitat needs of the Florida Manatee over the past several decades of focused research, starting with the treatise by Hartman (1979). Florida Manatee biology has been summarised nicely by Reep and Bonde (2021), and Marsh et al. (2011) have written a comprehensive scholarly review and synthesis of sirenian ecology. This section summarises some of the highlights of this body of knowledge for the Florida subspecies.

The movements of Florida Manatees are largely influenced by their need for food, thermal shelter in winter, freshwater for drinking, resting sites, and breeding. See Deutsch et al. (2022a, 2022b) for reviews of movement behaviour in Florida Manatees and other sirenians across a range of spatio-temporal scales. Manatees in the United States typically undertake long-distance migrations, resulting in seasonal shifts in geographic distribution of the population (Weigle et al. 2001, Deutsch et al. 2003b, Cloyed et al. 2021, Slone et al. 2022). These seasonal migrations are mostly driven by fluctuations in water temperature, with 20ᵒC being a critical limit (Hartman 1979, Bengtson 1981, Shane 1984, Deutsch et al. 2003b). The physiology of manatees is adapted to tropical waters; consequently, their very low metabolic rate and high thermal conductance make them vulnerable to illness and death when exposed to cold water temperatures (Irvine 1983, Bossart et al. 2002, Hardy et al. 2019). Individuals show strong fidelity (returning year after year) to seasonal ranges, including to specific warm-water sites used during cold weather (Rathbun et al. 1990, 1995; Reid et al. 1991; Koelsch 1997; Deutsch 2000; Deutsch et al. 2003b). These winter and warm season ranges are typically separated by lengthy travel corridors used during migration. There is evidence for natal philopatry, with movement patterns and seasonal ranges being passed on from mother to calf during the long dependency period (Deutsch et al. 2003b, 2022a; O’Shea et al. 2022). Manatees are individualistic in their movement behaviour, with considerable variation among individuals in range size, seasonal movement patterns (from residents to long-distance migrants), trigger temperature for migratory timing, degree of range and site fidelity, and time spent outside of warm-water refuges (Deutsch et al. 2003b, 2022a; Deutsch and Barlas 2016).

Another key characteristic of the Florida Manatee is that it is a generalist in many aspects of its ecology. Manatees can and do thrive in a large diversity of coastal and inland water bodies, including those fringed with mangroves or salt marshes and those in urban environments with dense human populations. They live in waters that range from freshwater to brackish to marine, although they regularly seek out freshwater sources to drink in estuarine and marine environments, where they are commonly found near the mouths of rivers (Lefebvre et al. 2001). Like all sirenians, Florida Manatees are herbivorous, but on rare occasions they have been observed to scavenge on dead fish or consume sessile aquatic invertebrates (Courbis and Worthy 2003). The varied environments that manatees occupy present them with a range of potential types of vegetation—benthic, emergent, floating, and bank—and, as generalist herbivores, they have a very broad diet (Etheridge et al. 1985, Smith 1993, Keith-Diagne et al. 2022). This includes seagrasses (especially Halodule wrightii or Shoal Grass, and Syringodium filiforme or Manatee Grass) and drift macroalgae in estuarine habitats, Smooth Cord Grass (Spartina alterniflora [now Sprobolus alterniflorus]) in salt marshes, and floating plants such as Water Hyacinth (Eichhornia crassipes) and submersed native or exotic vegetation (such as Hydrilla verticillata) in slow-moving freshwater bodies. Manatees and the habitats upon which they depend have certainly suffered a number of direct and indirect adverse impacts from human activities in the coastal zone (see Threats). But this aquatic mammal has also demonstrated an ability to adapt to and even take advantage of some human alterations to their natural habitats. Feeding on abundant, non-native invasive freshwater vegetation such as Eichhornia and Hydrilla is one example. Manatees often use dredged channels as travel corridors or to gain access to shallow feeding areas. Residential canals and other dredged basins are frequently used as quiet resting sites, and these sites sometimes even provide thermal benefit over nearby ambient waters during cold periods.

There are two exceptions to the manatee’s generalist habits. First, as noted above, manatees are restricted by water temperature, unable to tolerate prolonged exposure to low water temperatures, with 20° C being the lower limit of their thermoneutral zone (Worthy et al. 2000). Second, their coastal habitat is limited to a relatively narrow strip close to shore where they can find food, freshwater, and shelter; they are generally found in riverine or coastal waters within the 12-foot (3.7-m) depth contour. Even though manatees have been documented diving to depths of up to 16 m, a recent study has found that, on average, 78% of the time the manatee was no more than 1.25 m from the surface (Edwards et al. 2016).

Regional networks of warm-water habitats that provide sufficient thermal shelter to manatees during cold weather are critical to manatee overwinter survival in Florida (Flamm et al. 2012). These habitats can be classified into essentially three main types: (1) discharges of artesian groundwater from natural springs; (2) discharges of thermal effluent from industrial outfalls, primarily power generating stations; and (3) thermal basins that retain heat due to thermal inertia associated with depth (e.g., dredged basins) or to temperature-inverted haloclines (Stith et al. 2010), and that sometimes gain heat through groundwater seeps, stormwater inputs, or possibly microbial degradation of organic material in the sediment (Laist and Reynolds 2005a). The spatial extent, thermal quality, and reliability of these habitats vary within and across types, and this is most obvious during severely cold winters (e.g., Barlas et al. 2011, Stith et al. 2012). Natural springs are generally the most reliable, consistently discharging water at temperatures of 22–23° C. Manatees aggregate at warm-water refuges in large numbers during cold weather, often several hundred animals at a given site (Laist and Reynolds 2005a, 2005b; Laist et al. 2013), preferring sites that provide the best combination of thermal shelter and proximity to forage. Manatee dependence on these two key resources during winter results in a repeated movement pattern of central-place foraging; manatees make feeding forays from the warm-water site (the central place) to seagrass beds or other areas with aquatic vegetation for periods of hours to days and then return to that site for warmth (Bengtson 1981; Deutsch et al. 2003a, 2006; Deutsch and Barlas 2016; Haase et al. 2017, 2020).

Manatees are considered semi-social, usually found alone or in small groups where they rest, travel, socialise, or forage together (O’Shea et al. 2022). The only stable bond between individuals is that between mother and calf. Oestrous females can attract up to 20 or more males, forming a mating herd that lasts up to a few weeks and whose composition changes daily (Hartman 1979, Bengtson 1981, Rathbun et al. 1995). Most mating activity and births occur during the spring and summer (March to September) (Ackerman et al. 1995, O’Shea and Hartley 1995, Rathbun et al. 1995, Reid et al. 1995, Schwarz 2008); during this time, males search for oeestrous females, resulting in a much higher movement rate for males than females (Bengtson 1981, Deutsch et al. 2003b). Breeding is much less common in winter, as males undergo a period of spermatogenic quiescence during that season (Hernandez et al. 1995).

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T. manatus manatus (Antillean Manatee or Greater Caribbean Manatee)

The Antillean (Greater Caribbean) Manatee has a strong association with freshwater ecosystems, freshwater sources, and coastal marine estuaries throughout its range, from Mexico to Central America and South America (Morales-Vela et al. 2000, Olivera-Gómez and Mellink 2005, Castelblanco-Martinez et al. 2013, Tavares et al. 2020, Morales-Vela and Bahena-Basave 2023). Manatees inhabit turbid and complex freshwater environments (Marsh et al. 2011). In the Orinoco River, manatees are present more than 1,100 km from its mouth on the Atlantic coast (Castelblanco et al. 2009). In Belize, manatees also use the marine Turneffe Atoll, located offshore30 km from the mainland (Morales-Vela et al. 2000, Edwards et al. 2014). In the Greater Antilles, their habitat is primarily marine but closely associated with freshwater sources like river mouths, as occurs in Hispaniola, Puerto Rico, Jamaica, and Cuba (Dominguez-Tejo 2012, Drew et al. 2012, Alvarez-Alemán 2018, Mignucci-Giannoni et al. 2018).

Periodical movements of manatees associated with freshwater resources have been documented along different coastal areas (Marsh et al. 2011, Castelblanco-Martinez et al. 2013, Tavares et al. 2020, Morales-Vela and Bahena-Basave 2023). In rivers, lakes, flood plains, and wetlands of Mexico, Belize, and Colombia, manatee distribution and movements are also associated with temporal changes in the annual rainy and dry seasons (Puc-Carrasco et al. 2017, Rodas-Trejo et al. 2008). Deutsch et al. (2022a) describe three types of seasonal movement patterns that manatees show in relation to seasonal changes in rainfall and associated water levels in freshwater and estuarine ecosystems.

Manatees' diverse diet has adapted to different environments, including freshwater, estuarine, and marine plants (Alves-Stanley et al. 2010, Keith et al. 2022). They have also adapted to consume submerged, emergent, floating, and riverbank vegetation that influences their seasonal distribution (Pablo-Rodriguez et al. 2015). Manatees from Puerto Rico and Belize have a diet composed primarily of seagrasses (Mignucci-Giannoni and Beck 1998, Alves-Stanley et al. 2010). Five species of seagrasses, red mangroves, and algae were some of the items identified as part of the diet of manatees in Puerto Rico, Belize, and Mexico (Mignucci-Giannoni and Beck 1998, Flores-Cascante et al. 2013).

For more information about general ecology and habitat, review the book Ecology and Conservation of the Sirenia (Marsh et al. 2011).

Information on threats is provided below separately for each subspecies.

Trichechus manatus latirostris (Florida Manatee)

Threats encompass extreme natural events and anthropogenic factors that can reduce reproduction, survival rates, or the carrying capacity of the environment. Manatees occupy habitats in the same coastal zone and inland waterways where humans recreate and carry out other activities, a fact that contributes to manatee vulnerability to human pressures. According to the U.S. Census Bureau (2020), Florida’s human population grew by 66% to an estimated 21.5 million from 1990 to 2020; projections suggest that the human population of Florida will increase to over 26 million people by 2040 and 34 million by 2070 (Carr and Zwick 2016, Rayer and Wang 2020). This is likely to increase risk to manatees from human-related activities. Potentially catastrophic threats to manatees include exposure to cold temperatures, harmful algal blooms, seagrass loss, hurricanes, and emergent disease. Climate change may also threaten Florida Manatees over the long term (Edwards 2013) by exacerbating the above threats or creating others. Here we group threats into direct ones that result in mortality or injury and indirect ones that degrade important manatee habitat.

Direct Threats to Florida Manatees: Manatees are injured or killed by several types of human-related activities. Besides collisions with vessels, described below, another documented threat is entanglement in fishing gear (crab pot line, monofilament line) or debris and incidental ingestion of marine debris that injures or blocks the gastrointestinal tract (Beck and Barros 1991, Adimey et al. 2014, Reinert et al. 2017). Entanglement rarely results in mortality but often causes disfiguring injuries, even amputation of a pectoral flipper. Manatees also die from entrapment in water-control structures and stormwater pipes, and from crushing in flood-control structures, in canal locks, or between large ships and docks (Ackerman et al. 1995, FWC 2007).

Boat Strikes: Watercraft collisions have accounted for an average of 21.1% (min – max = 8.8 – 31.1% across years) of all reported manatee deaths and 29.9% (16.0 – 39.9%) of deaths of known cause from 2000–2019, and this is the single greatest cause of human-related mortality (Deutsch and Reynolds 2012; FWC manatee mortality data, https://myfwc.com/research/manatee/rescue-mortality-response/statistics/mortality/). The proportion of adult deaths due to boat collisions is much higher than in immature age classes (Deutsch and Reynolds 2012, Runge et al. 2017), which is significant because adult survivorship is the principal driver of manatee population dynamics (Runge et al. 2004). The number of registered vessels in Florida increased by an average of 2.9% per year over 25 years, topping one million boats by 2007 (FLHSMV, https://www.flhsmv.gov/motor-vehicles-tags-titles/vessels/vessel-owner-statistics/). Those numbers declined over the subsequent seven years due to an economic recession, but they have resumed a gradual increase since 2013, reaching 1,029,993 vessels by 2022. In addition, thousands more visitors ply Florida’s waterways with out-of-state vessels. Given that about 97% of registrations are for recreational watercraft (Wright et al. 1995; FLHSMV, https://www.flhsmv.gov/motor-vehicles-tags-titles/vessels/vessel-owner-statistics/), it is reasonable to expect a continued increase in recreational vessels on Florida’s waterways with a concomitant increase in the human population.
In addition to the expected increase in boat numbers over the coming century, there are other factors that may act synergistically to increase the risk of lethal collisions between manatees and watercraft. Modifications to the design of vessel hulls and engines have allowed boats to travel at higher speeds in shallower waters (Wright et al. 1995), thus threatening manatees and scarring seagrass beds. The weight of evidence indicates that faster boats pose a greater risk of collision with manatees than do slow-moving boats, because manatees have less time to respond to boats moving at planing speeds (Calleson and Frohlich 2007; Rycyk et al. 2018, 2022). Boater compliance with posted speed zones has averaged about 50-60% in a few studies, but it varies greatly across sites, vessel type and size, and other factors (Shapiro 2001, Gorzelany 2004). Some waterways experienced 85% compliance rates and others as little as 14% (Gorzelany 2013). Increased law enforcement patrols and establishment of a general boater licensing programme would likely increase the effectiveness of the regulations adopted to protect manatees from collisions.

Sub-lethal effects on manatees of increased vessel traffic and a growing human population in the coastal zone are also cause for concern. A detailed study of Florida Manatee carcasses recovered in Florida over a 10-year period (2007–2016) by Bassett et al. (2020) found that 96% of adult carcasses bore scars from previous boat collisions and about ¼ of adult carcasses showed evidence of 10 or more separate watercraft strikes. This level of sublethal trauma from boat strikes is greater than in any other marine mammal than has been studied. The healed, skeletal fractures in some carcasses indicate that the animals had survived previous traumatic impacts (Wright et al. 1995, Lightsey et al. 2006). Of over 1,000 living individuals in the manatee photo-identification database (Beck and Reid 1995), 97% had scar patterns from multiple boat strikes (O’Shea et al. 2001). Many of these individuals were severely mutilated, especially on the tail and the dorsum. Non-lethal injuries may reduce the breeding success of wounded females and may permanently remove some animals from the breeding population (O’Shea 1995, Reynolds 1999), although that effect has not been investigated. Vessel traffic and recreational activities that disturb manatees may cause them to leave preferred habitats and may alter biologically important behaviours such as feeding, nursing, or resting (O’Shea 1995, Wright et al. 1995). This may explain why manatees preferentially select seagrass habitats with lower levels of low-frequency (<1 kHz) ambient noise (Miksis-Olds et al. 2007).

Cold Events: Manatees seek warm-water sites when temperatures drop below 20^o C and are unable to tolerate prolonged exposure to temperatures below about 16^o C (Irvine 1983). Major spikes in cold-related manatee deaths have been documented during cold winters numerous times (O’Shea et al. 1985, Ackerman et al. 1995, Hardy et al. 2019). An unusual mortality event (UME) during winter 2009-10 was unprecedented in its scale and spatial scope, with 480 manatee carcasses reported state-wide during its three-month timeframe; 89% of deaths for which cause could be determined were due to cold stress (Barlas et al. 2011). Death from exposure to cold can occur acutely, from hypothermia, or from chronic exposure. Manatees chronically exposed to water temperatures below 20^oC display a range of clinical and pathological signs such as emaciation, oedema, serous atrophy of fats, and dehydration (O’Shea et al. 1985, Bossart et al. 2002). Calves and subadults are the most vulnerable to cold-related death (O’Shea et al. 1985, Ackerman et al. 1995). Unless management is proactive about replacing lost industrial warm-water refuges or in otherwise mitigating the negative impacts resulting from loss of natural and human-made warm-water habitats, we can expect higher cold-related mortality during cold winters in the future (Laist and Reynolds 2005b).

Red Tide: Manatees in Florida’s southwest region are frequently exposed to and die from brevetoxin, a potent neurotoxin produced by the dinoflagellate Karenia brevis, during “red tide” blooms (O’Shea et al. 1991, Bossart et al. 1998, Landsberg and Steidinger 1998, Flewelling et al. 2005). Red tide blooms have resulted in major manatee mortality events 12 times between 1982 and 2022 (all except one since 1996), likely killing over 1,400 manatees (FWC, unpublished data). The largest mortality events to date occurred during red tide blooms in the calendar years of 2013 and 2018, resulting in the deaths of 277 and 288 manatees, respectively, within the boundaries of the blooms in southwest Florida (FWC, unpublished data, https://myfwc.com/research/manatee/rescue-mortality-response/statistics/mortality/red-tide/). These mortality events can have noticeable impacts on survival rates, and hence, on population growth (Runge et al. 2017, Hostetler et al. 2021). For example, the large red tide mortality event of 2013 was estimated to cause abundance in the SW region to decline by 11% (95% CRI, 7–15%), in contrast to an increase of 2% (1–3%) in an average year (Hostetler et al. 2021). Over the past quarter century, manatee mortality events due to red tide have occurred in the SW region about every other year (Martin et al. 2017; FWC, unpublished data). Forecasts from an expert panel suggest that manatee die-offs from harmful algal blooms will probably become more frequent in the future (Martin et al. 2017) because of ocean warming due to climate change, coastal nutrient loading, and other factors (e.g., Hallegraeff 2016, Gobler 2020, Griffith and Gobler 2020, Medina et al. 2022).

Hurricanes: Hurricanes are another type of weather-related catastrophe that can potentially impact manatee populations and their habitats. Manatees can be stranded or entrapped in small ponds by surge waters. In the northwest region, apparent adult survival rate was lower in years with severe storms or hurricanes (Langtimm and Beck 2003). Such events could also result in permanent, large-scale emigration. In eastern Australia, for example, the simultaneous occurrence of flooding and a cyclone, combined with poor watershed management practices, resulted in the loss of 1,000 km² of seagrass beds and in the mass movement and mortality of Dugongs (Dugong dugon) (Preen and Marsh 1995), a sirenian relative of the manatee. The increased runoff associated with hurricanes in Florida has also been shown to reduce water visibility and salinity, and to result in declines in submerged aquatic vegetation (SAV) coverage (e.g., Ridler et al. 2006, Carlson et al. 2010).

Disease: Large-scale mortality events caused by disease have decimated other populations of marine mammals, including seals and dolphins, often removing 50% or more of the individuals (Harwood and Hall 1990). No such epizootics have been documented in manatees, but the population has been exposed to pathogens—such as Toxoplasma gondii (Buergelt and Bonde 1983, Smith et al. 2016) and morbillivirus (Duignan et al. 1995)—that have been responsible for mortality events in other marine mammal species (e.g., Lipscomb et al. 1994, Dubey et al. 2003). Spread of such pathogens could be particularly rapid during winter when manatees are densely concentrated in warm-water refuges and when their immune systems may be compromised by exposure to cold (Walsh et al. 2005). Thus, the emergence of a serious infectious disease poses a potential threat to the population (Runge et al. 2017).

Threats to Florida Manatee Habitat: Manatees require forage, thermal refuges in the winter, quiet resting areas, and freshwater. Here we focus on threats to habitats that provide warm-water shelter and forage.

Threats to Warm-water Habitat: Expected changes to the warm-water network over the next several decades likely present the most serious habitat threat to manatees in Florida over the long term; if unmitigated, these changes will likely result in higher cold-related mortality and lower carrying capacity (Laist and Reynolds 2005a, 2005b; Runge et al. 2017). Manatees have used the thermal effluents of power plants in winter for over six decades and now a large proportion of the population in the SW and ATL regions rely on them for warmth (Laist et al. 2013). Eventual retirement of these power plants or future elimination of the once-through cooling technology permitted by regulatory agencies threatens the reliability and existence of these warm-water sites (Laist and Reynolds 2005b). The increasing establishment of utility-scale clean energy sources, such as solar farms, are accelerating these trends and will likely lead to less reliable thermal discharges sooner than previously expected. Several industrial thermal outfalls used by manatees, including those from power plants, have already been eliminated. Furthermore, artesian spring flows have declined, and water quality has been degraded (high nitrogen), leading to overgrowth of noxious algae and loss of native vegetation, in many spring runs; these trends will likely continue as demand for water increases with continued growth in the human population (Florida Springs Task Force 2000). Declining flows will provide less warm-water habitat for wintering manatees, particularly in the NW and USJ regions where they are nearly entirely dependent on spring flows for thermal refuge. In addition, dams and other structures currently impede or prevent manatee access to a number of spring systems (Taylor 2006).

Threats to Forage Habitat: Human development in the coastal zone over the past century has often negatively impacted manatee foraging habitat, due to loss of seagrass beds directly from dredge-and-fill activities and indirectly through nutrient loading and reduced water clarity (Fonseca et al. 1998). Declines in water quality (e.g., increased nitrates) due to sewage releases during storms or other events, non-point source runoff (e.g., from agriculture, urban areas), and groundwater nutrient inputs (e.g., from septic tanks) can promote the growth of undesirable macroalgae, such as Anadyomene spp. in estuarine systems (Santos et al. 2020) and the unpalatable blue-green alga Lyngbya sp. in freshwater systems (Hudon et al. 2014), which can smother food plants used by manatees (Florida Springs Task Force 2000). Such increases in nutrients also promote dense, single-celled algal blooms, which can shade out seagrasses and other submerged aquatic vegetation (Phlips et al. 2015, 2021; Trefry and Fox 2021). Vessel traffic can also degrade SAV through increased water turbidity from wake action and scarring of shallow seagrass beds by propellers and anchors (Sargent et al. 1995).

Unprecedented seagrass losses in the Indian River Lagoon—a 250-km long biodiverse estuary along the central-east coast of Florida—have been occurring since 2011 due to prolonged and repeated algal blooms that block sunlight from reaching benthic plants, resulting in seagrass mortality (Phlips et al. 2015, 2021; Morris et al. 2018, 2022; Lapointe et al. 2020). Between 2009 and 2021, the IRL lost about 24,000 hectares of seagrass habitat, a 75% reduction in areal extent; and by 2020, the mean per cent seagrass cover within that footprint had declined by 89%, from ~20% to ~2%, on average (St. Johns River Water Management District (SJRWMD), unpublished data). So over 95% of seagrass biomass in the IRL has been lost during this period. Seagrass has essentially disappeared in many areas, leaving mostly bare sandy substrate where there had once been lush meadows of seagrass and drift macroalgae. These catastrophic losses of SAV have dramatically reduced the forage-based carrying capacity of this vital lagoon system for manatees and have resulted in mass starvation and mortality of manatees (FWC 2023a; see section on Unusual Mortality Event in the Atlantic Coast Region under Population). The northern IRL is the major year-round hub of manatee activity on the east coast (Deutsch et al. 2003b), including for migrants both north and south of the region, which is why the consequences of seagrass loss here for manatees have extended throughout the entire Atlantic coast region (Deutsch et al. 2021, FWC 2023b). Limited availability of forage resulted in manatees that summered in the IRL entering winter in depleted poor body condition (FWC 2023b). This made the animals more susceptible to the effects of cold, including cold stress syndrome and mortality.

Loss of seagrass has been documented to result in manatee mortality through a more indirect route as well. After the “superbloom” of phytoplankton in the Indian River Lagoon in 2011, the area and biomass of seagrass declined sharply. In 2013 a variety of macroalgae became abundant and many manatees in the region shifted to feeding on these algae (Allen et al. 2022). An unusual mortality event soon followed, with apparently healthy manatees in good body condition dying suddenly from an unknown cause. After years of exhaustive investigations, it was determined that this dietary shift led to dysbiosis (disruption of the gut microbiome) and clostridial infection that resulted in acute death of some manatees (Landsberg et al. 2022).

Furthermore, seagrass has also declined along nearly all of Florida’s east coast, from the lower St. Johns River in the north to Biscayne Bay and Florida Bay in the south and many intracoastal waterways in between (e.g., Collado-Vides et al. 2013, Hall et al. 2016, Orlando et al. 2016, Marine Resources Council 2018, Morris et al. 2018, Kahn 2019). The substantial loss of beds of Vallisneria and other native freshwater SAV in the lower St. Johns River, extending well into the upper St. Johns basin at least as far as Lake George (SJRWMD, unpublished data), is also concerning, as that stretches into another manatee management unit (subpopulation). Although seagrass beds have generally been expanding over the years in estuaries along Florida’s Gulf coast (Tomasko et al. 2018), recently the trend has reversed in a number of important areas. In some cases, this has been associated with replacement by the rooted macroalga Caulerpa prolifera (e.g., parts of Tampa Bay) and in other cases by extensive blooms of drift macroalgae (e.g., Charlotte Harbour) (see presentations from 2021 Florida Macroalgae Workshops, https://sarasotabay.org/2021-macroalgae-workshops/). These developments serve as a cautionary note about how quickly positive habitat trends can shift in worrisome directions.

Climate Change Impacts to Habitats: The potential effects of climate change on sirenians are myriad (Edwards 2013), but there have been no analyses to test potential hypotheses. Effects on the occurrence and severity of harmful algal blooms are noted above. If the overall warming trend leads to consistently warmer winters in Florida, then we might expect a reduction in cold-related mortality. Rising water temperature poses a direct threat to seagrasses if it reaches the plant’s physiological tolerance or otherwise reduces productivity (Barber and Behrens 1985, Short et al. 2016). Increased frequency of extreme weather events is also likely to reduce forage habitat in coastal areas (Babcock et al. 2019), with consequent impacts on sirenians (e.g., Preen and Marsh 1995, Preen et al. 1995). Of concern in Florida, sea level rise will cause the shrinkage of seagrass beds at their outer depth limits in areas where armouring of the shoreline prevents shoreward migration, in what is known as ‘coastal squeeze’ (Short and Neckles 1999, Doody 2004). This situation will likely occur along most of the developed shorelines in Florida and may get worse as state and local governments and residents attempt to protect infrastructure, homes, and commercial developments from rising seas. Finally, higher water levels may suppress flow of coastal springs, further reducing warm-water habitat. Many other cascading impacts on manatees from disruption of the climate system are possible (Edwards 2013, Marsh et al. 2022), but the uncertainties are great.

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T. manatus manatus (Antillean Manatee or Greater Caribbean Manatee)

Anthropogenic Threats

Antillean (Greater Caribbean) Manatees are threatened throughout their range by various pressures, mainly of anthropogenic origin. They include poaching, habitat loss, chemical pollution, entanglement, and boat collisions (UNEP 2010). Some threats have been reduced, others have increased, and new threats are emerging. The common factors are uncontrolled human activity and extensive coastal development, habitat encroachment, inadequate funding to support research to evaluate threats, the poverty and poor socio-economic conditions present in several Latin American countries, and limited implementation of effective conservation actions.

Poaching
Historical poaching was reported in almost all countries where the subspecies is distributed (i.e., Durand 1950, De Landa 1978, McKillop 1985, Mignucci-Giannoni et al. 2000,Lefebvre et al. 2001, Montoya-Ospina et al. 2001, Jiménez-Pérez 2002, de Thoisy et al. 2003, Morales-Vela et al. 2003, UNEP 2010, Marsh et al. 2011, Bonde et al. 2012). Currently, manatee hunting for consumption continues to occur in some countries and, in some cases, for meat trading. Conditions of extreme poverty in some countries have forced fishers, local people, and some indigenous communities to see manatees as a source of food and income. Other uses include traditional medicinal purposes and the use of bones to fabricate various implements (Auil 1998, Dominguez-Tejo 2016). Due to the manatee’s low abundance in many parts of their range, poaching is generally restricted to opportunistic catches. Poaching is still a threat on the north and northeast coasts of Brazil (J.C. Borges pers. comm. 2018), and in Belize (Z. Walker pers. comm. 2018), Colombia (B. Aguilar and D. Caicedo pers. comm. 2018), Cuba (Alvarez-Alemán et al. 2018, 2021), Dominican Republic (Dominguez-Tejo 2016), Guatemala (Machuca-Coronado et al. 2023), Haiti (Mignucci-Giannoni and Aquino 2020) and Nicaragua (A. Mignucci-Giannoni pers. comm. 2021). The situation in Venezuela (Ferrer et al. 2017) is also of great concern as there are recent reports of hunting, including: in 2020, two manatees were killed in the Maracaibo Lagoon (Y. Briseño pers. comm. 2021); and from November 2020 to January 2021 approximately 20 manatees were hunted in Sucre, in the Turuépano National Park (G. Mendez pers. comm. 2021). In Haiti, of the 11 manatees that were sighted and reported between 2019 and 2021, eight were killed and butchered for selling the meat for food (Mignucci-Giannoni and Aquino 2019; J. Aquino pers. comm. 2021).

Habitat Loss
The distribution of the Antillean (Greater Caribbean) Manatee is extensive but highly fragmented, and the lack of habitat connectivity combined with low reproductive rates has significantly affected its overall population viability. Conservation of coastal habitats and migration corridors is important to maintain populations. For example, the stranding of dependent calves is one of the leading causes of mortality in the northeast region of Brazil, presumably because pregnant females are not gaining access to quiet and protected estuarine waters to give birth due to habitat degradation (Luna et al. 2012). In the Caribbean region, coastal zone development has increased due to tourism, urbanisation, and the oil and transportation industries. Coastal development in Belize has promoted the removal of littoral forests, seagrass destruction by dredging of canals, and mangrove destruction by the construction of seawalls (Auil 1998).

Other human activities such as agriculture, logging, and ranching have led to sediment build-up along rivers and coastal lagoons in Costa Rica (Smethurst and Nietschmann, 1999) and Brazil (Lima de et al. 1992). In Colombia, the rapid increase of wetlands sedimentation in some river basins with high densities of manatees could represent a significant threat to the species in the dry season (B. Aguilar pers. comm. 2018). In flood-pulse river systems, manatees are forced to migrate due to the pronounced seasonal fluctuations in water level (Deutsch et al. 2022a). Their migratory routes include shallow segments that can act as bottlenecks during the low-water season, a problem exacerbated by sedimentation caused by human activities in the riparian zone. For example, in Catazajá, Mexico, several manatees were trapped in shallow lagoons during the dry season (Alejandro Ortega-Argueta pers. comm. 2024). This phenomenon impedes the passage of manatees to refuge areas, increasing the probability of death and stranding and making them vulnerable to hunters (Castelblanco-Martínez pers. comm. 2018). Other consequences of agricultural practices are modification of river pathways and destruction of riparian and shoreline vegetation (Lima de et al. 1992).

Dredging of canals and channels to promote vessel traffic and shipping for industrial or tourism activities may have significant consequences on habitat connectivity and ecological structure (Hernández-Arana and Ameneyro-Angeles 2011). Manatees inhabiting or migrating through nearshore areas have the potential to travel through a wide range of channel types, facing a greater abundance of vessels than previously recognised (Cloyed et al. 2019). This has been raised as an issue across several areas used by manatees in the Caribbean region.

Invasive Species
Introduced aquatic species, including animals and plants, could potentially affect manatee habitat. It is particularly concerning that the introduced population of hippopotamuses (Hippopotamus amphibius) in the Magdalena River basin, a manatee habitat in Colombia, has increased from four in 1981 to over 80 individuals (S. Monsalve pers. comm. 2019). It is predicted that between 400 and 800 hippopotamuses could be present by 2050 if the uncontrolled population continues to increase and spread into the swamps of the middle Magdalena River basin (Subalusky et al. 2019).

An invasive seagrass has recently been discovered in the Caribbean and Puerto Rico (Mignucci 2019). This is a seagrass from the Red Sea and the Indian Ocean named Broad-leaf Seagrass (Halophila stipulacea). The marine plant is now spreading rapidly in different parts of Puerto Rico, particularly in the waters of Culebra, Ceiba, and Jobos Bay, the latter two being primary habitats for manatees. Biologists from the Department of Natural and Environmental Resources (DNER) and the U.S. Fish and Wildlife Service are concerned that it may outcompete and displace local populations of the other naturally occurring seagrasses.

Chemical Pollution
Chemical pollution is an issue in countries with extensive agricultural industries, such as Costa Rica (Jiménez-Pérez 1999) and Belize (Takeuchi et al. 2016). Chemical pollutants such as per- and poly-fluoroalkyl substances (PFAS) have been found in manatees from Puerto Rico (Palmer et al. 2019). High levels of polychlorinated biphenyls (PCBs) have been found in manatees from Chetumal Bay, Mexico, indicating a potential risk to health (Wetzel et al. 2012). Concentrations of heavy metals in manatees from the Gulf of Mexico, the Mexican Caribbean, and Brazil were significantly higher than those reported in other marine mammals (Anzolin et al. 2012, Romero-Calderón et al. 2016). Arsenic concentrations were higher in manatees from Belize than those from Florida (Takeuchi et al. 2016).

The oil industry has been identified as a major threat in several countries with a high abundance of manatees. In Mexico, long-term exposure to pollutants derived from the oil industry may be the primary source of metals accumulation in manatee bones in Tabasco and Campeche states, in the Gulf of Mexico (Romero-Calderón et al. 2016). In Belize, oil exploration, oil spills, and drilling are identified as one of the highest threats because of the potential impacts (Ortega-Argueta et al. (in prep.). In Brazil, an extensive oil spill spread over nearly 1,000 beaches along about 3,000 km of the Maranháo state coastline in 2019, which is considered the last major stronghold for manatees in Brazil (Siciliano et al. 2020). This has been considered perhaps the worst environmental disaster in Brazil's coastal zone.

Entanglement and Fisheries Interaction
Bycatch of manatees occurs in most countries throughout the subspecies' range, but at a relatively low level (Kiszka 2014). This threat has been reported in Nicaragua (Jiménez-Pérez 2002), Costa Rica (C. Espinoza pers. comm. 2018), Brazil (J.C. Borges pers. comm. 2018), Venezuela (Ferrer et al. 2017), Colombia (B. Aguilar pers. comm. 2018), Mexico (SEMARNAT 2020), Cuba (Alvarez-Alemán et al. 2018, 2021), and Dominican Republic (H. Dominguez-Tejo pers. comm. 2018), among others. Incidental death in fishing nets is one of the main causes of manatee mortality in areas of South America (Castelblanco-Martínez et al. 2009); in Guatemala this is considered to be the second highest mortality threat (Machuca-Coronado et al. 2023).

Debris
Ingestion of marine debris has been identified as a threat to the health of rehabilitated and released manatees in Brazil, where plastic debris ingestion was confirmed in 10% of the animals examined (Attademo et al. 2015). The same study considers that debris-related mortality is a cryptic problem that is difficult to evaluate due to the low probability of finding intact manatee carcasses with evidence of debris ingestion. Types of debris identified in manatees in the Mexican Caribbean include plastic, cloth, and glass (K. Arévalo-González pers. comm. 2020).

Watercraft Collisions
Collisions with watercraft are relatively uncommon throughout the manatees' range, except for Belize, Puerto Rico, Dominican Republic, Mexico, and Brazil (Mignucci-Giannoni et al. 2000; Borges et al. 2007; Bonde et al. 2012; Dominguez-Tejo 2016; Castelblanco et al. 2020; Galves et al. 2022, 2023). In Costa Rica, the construction of a new maritime station in the Moin area increases the potential risk to manatees (C. Espinoza pers. comm. 2018).

Puerto Rico and Belize are the only countries where boat collisions have resulted in historically high manatee mortality. In Puerto Rico, watercraft-related mortalities include propeller strikes and jet-ski collisions (Mignucci-Giannoni et al. 2000, Bonde et al. 2012; Caribbean Manatee Conservation Center unpublished data). Death from watercraft collision represented 18% of manatee carcasses in Puerto Rico between 1974 and 1995 (or 24% of those with known cause of death), becoming more common after 1990 (Mignucci-Giannoni et al. 2000); but it accounted for half of manatee mortality in 2020 and 2021.

Watercraft collision has become the leading cause of manatee strandings (live and dead) in Belize, accounting for 35% of such events since 2010 (Galves et al. 2023). The first recorded death due to a boat strike was documented in 1997, but the number of manatees killed by boats increased sharply starting in 2013, which corresponds to an increase in the number of tourists visiting Belize (Galves et al. 2022). The annual number of manatees strandings attributed to watercraft collisions peaked at 17 in 2017, representing 47% of the total number that year. Galves et al. (2023) found that strandings were greatest in areas of high boat traffic and high human activity, especially in the waters around Belize City and Placencia; in fact, 78% of collision-related strandings occurred in the busy Belize City sector, where 21% of boats registered in the country were located.

Natural Threats

Harmful Algal Blooms
In 2018, an unusual mass mortality event occurred in a freshwater system in Tabasco, Mexico. At least 48 manatee carcasses were found, representing at least ~7.4% of the estimated manatee population in this region. The causes were undetermined; however, the presence of blue-green algae species with the capacity to produce toxins (microcystin and saxitoxin, both regularly found in cyanobacterial blooms) was detected in the water quality assessment in several places (Morales-Vela et al. 2018). Microcystin was detected in only one manatee carcass at a low concentration (Benjamín Morales pers. comm. 2018), similar to the lowest levels reported in California sea otters killed by microcystin poisoning (Miller et al. 2010). Harmful cyanobacterial algal blooms---which are exacerbated by the increased nutrient loading of water bodies from agriculture (Paerl et al. 2016)---are predicted to become more frequent with global warming and the associated warming of aquatic ecosystems. This mortality event could represent the emergence of a serious new threat to manatees in tropical freshwater ecosystems throughout their range. From June to August 2023, a similar event occurred again in that region of Mexico, resulting in the death of at least 30 manatees (Darwin Jimenez pers. comm. 2023).

Hurricanes
Hurricanes and major storms bring high winds, high precipitation, and strong storm surge, and they can strand manatees when the water recedes, potentially reducing manatee survival rates (Langtimm et al. 2006) and adversely impacting their foraging habitats (Ridler et al. 2006). For the Antillean (Greater Caribbean) Manatee, the effects of intense hurricanes need to be evaluated. In 1988, the northeast coast of the Yucatán Peninsula, Mexico, was severely impacted by Hurricane Gilberto (category 5), causing great devastation and loss of SAV in the estuaries. Local fishermen in the Yalahau Lagoon north of Cancun observed that this hurricane devastated the entire bottom of the lagoon, affecting the “cevadales” (seagrasses) that manatees eat. They believed that the manatees left this lagoon due to insufficient food (Morales-Vela and Humberto-Bahena 2023). In fact, manatees were not observed on the northeast coast of the Yucatán Peninsula for many years after the hurricane (Morales-Vela and Olivera-Gómez 1997, Morales-Vela et al. 2003) until August 2006, when six adults were reported (Reyes-Mendoza and Morales-Vela 2007).

Pathogens
The overall health status of the subspecies and the impact of infectious diseases on the population have not been well investigated (Sulzner et al. 2012). Manatees are susceptible to water- and arthropod-borne infections while they are in shallow waters close to shore in areas with dense human populations (Vélez et al. 2019). A variety of parasites, some of them considered as anthropozoonotic, have been reported in Brazil (Carvalho et al. 2009, Borges et al. 2011, Borges et al. 2017), Mexico (Hernández-Olascoaga et al. 2017), Puerto Rico (Mignucci-Giannoni et al. 1999a, Colón-Llavina et al. 2009, Bossart et al. 2012, Wyrosdick et al. 2018), Cuba (Coy Otero 1989), Dominican Republic (Mignucci-Giannoni et al. 1999b), and Colombia (Vélez et al. 2018, 2019). Parasite species include protozoan (Eimeria nodulosa, E. manatus, Entamoebasp.and Giardia sp.), trematode (Chiorchis fabaceus, C. groschafti, Moniligerum blairi, Pulmonicola cochleotrema, Nudacotyle undicola), and nematode (Heterocheilus tunicatus and species in the Ascarididae). Heavy parasitic loads in manatees are common, but generally not of pathologic concern (Bonde et al. 2012).

Evidence for infection of manatees with Toxoplasma gondiiin Puerto Rico (Bossart et al. 2012, Wyrosdick et al. 2017), Belize (Sulzner et al. 2012), and Brazil (Attademo et al. 2016) suggest that toxoplasmosis may be an emerging threat for certain populations of this subspecies. In Puerto Rico, the prevalence of T. gondii infection in feral cats is a cause for concern; the mechanism of transfer of this terrestrial parasite to manatees (Bossart et al. 2012), including the presence of this protozoan in seagrasses (Wyrosdick et al. 2017), needs investigation. Evidence for leptospirosis, a worldwide zoonosis affecting many wild and domestic animals, was also found in manatees from Belize (Sulzner et al. 2012) and Mexico (Aragón-Martínez et al. 2014), including antibody titers for Leptospira bratislava, L. canicola, L. icterohemorrhagiae (Sulzner et al. 2012) and L. interrogans (Aragón-Martínez et al. 2014). In Brazil, several bacteria were identified in blood samples from Antillean (Greater Caribbean) Manatees (Silva et al. 2017) and a manatee calf died due to a case of salmonellosis infection caused by Salmonella panama (Vergara-Parente et al. 2003).

Other Diseases
Few studies have been published about diseases in T. manatus manatus; however, some reports exist about cerebral and cardiac congenital malformations (Moore et al. 2008, Carvalho et al. 2019), fibro-purulent pneumonia, and chronic kidney disease (Klećkowska-Nawrot et al. 2019).

During a biomedical assessment of manatees in Chetumal Bay, Mexico in 2021, researchers examined a female with a tumour-like fibropapillary lesion on her genitals, potentially papillomavirus-type (Morales-Vela and Bahena-Basave 2023). This is the first case seen in Chetumal Bay in more than 80 manatees that have been medically evaluated. In 2007, negative results for papillomavirus (TmPV1) antibodies were obtained from a serological evaluation of 21 manatees from Chetumal Bay (Morales-Vela and Padilla-Saldivar 2009). The same assessment conducted in Belize detected low levels of anti-TmPV1 antibodies in a few animals but without evidence of papillomatosis (Dona et al. 2011). In 2020, a novel manatee papillomavirus (TmPV5) was isolated in a manatee from Puerto Rico (Mignucci-Giannoni et al. 2022). It is necessary to continue with the biomedical evaluation of manatee populations to detect, identify, and prevent potential infectious diseases.

There is no commercial utilisation of West Indian Manatees. Subsistence utilisation (i.e., hunting) is occasional in some regions. Throughout much of the range of the Antillean (Greater Caribbean) subspecies, illegal hunting (poaching) is carried out mainly for the consumption of meat; other parts are used for medicinal purposes and bones are sometimes used for making tools or adornments (Aragones et al. 2012); see section on anthropogenic Threats.

Non-consumptive use

Trichechus manatus latirostris: Florida Manatees have become the centre of a large ecotourism industry at certain winter aggregation sites, such as Crystal River. Tens of thousands of people visit these areas annually to observe and swim with manatees, creating challenges for management (Sorice 2003). No-entry sanctuaries provide manatees with havens to avoid swimmers and boats at some of these sites (Buckingham et al. 1999). At other sites, groups of paddlers (e.g., on kayaks) or swimmers can cause considerable disturbance to manatees trying to rest and conserve energy.

T. manatus manatus: Manatee-watching has been growing as a local economic alternative in several countries, including Belize, Costa Rica, the Dominican Republic, Mexico, Panama, Puerto Rico, and Brazil. In almost all cases, this activity provides alternative income to local communities and opportunities for the sale of various handicrafts. Swimming with manatees is also offered by some private parks where manatees are held in captivity. These activities need to be carried out with specific regulations to avoid negative impacts, however; this presents , a challenge for management in several countries that lack such regulation. Often, the success of manatee-watching activities is associated with the participation of local communities, the support of environmental organisations, and the active involvement of managers and researchers.

Information on conservation is provided below separately for each subspecies.

Trichechus manatus latirostris (Florida Manatee)

The West Indian Manatee, including both subspecies, is protected under United States federal legislation through the Endangered Species Act (ESA) of 1973 and the Marine Mammal Protection Act of 1972. At the state level, the Florida Manatee Sanctuary Act of 1978 provides the framework for the establishment of a number of important regulatory protections for manatees, such as boat speed rules. Numerous actions by state and federal agencies related to research and monitoring are not included in this section but can be found elsewhere (USFWS 2001, FWC 2007, Deutsch and Reynolds 2012).

The Florida Manatee is a conservation-reliant species, which means that the sustainability of the population is supported by active conservation programmes. There is a high degree of interaction (both direct and indirect) between manatees and a variety of human activities in a state where coastal development and human population density are high and increasing. Large and active research and management programmes at federal, state, and county levels have been implemented to reduce watercraft-related and other human-caused mortality (e.g., through speed restriction zones and sanctuaries), to protect and restore key warm-water habitats, and to rescue, rehabilitate and release injured or sick manatees (USFWS 2001, FWC 2007). The PVA described in the population section of this red list assessment assumes that existing protections, regulations, rescue and rehabilitation programmes, and enforcement continue into the future (Runge et al. 2017). Reduction or elimination of such conservation efforts and protections would likely halt or reverse the trend in population recovery that has occurred over the past several decades.

Efforts to Reduce Watercraft-related Injuries and Deaths

The largest cause of manatee death over which managers have some control is watercraft collision. Many living manatees bear scars or wounds from vessel strikes (Bassett et al. 2020). Because watercraft operators cannot reliably detect and avoid hitting manatees, federal and state managers have sought to limit watercraft speed in areas where manatees are most likely to occur to give both manatees and boaters more time to avoid collisions (Calleson and Frohlich 2007). Speed zones can be quite effective at reducing the risk of lethal collisions (Udell et al. 2018). Since 1989, state and local governments have cooperated in the development and implementation of county manatee protection plans—which, among other things, affect vessel traffic patterns through boat facility siting—and manatee protection speed zone rules (FWC 2007). Two types of manatee protection areas also have been established by the federal U.S. Fish and Wildlife Service (USFWS): (1) manatee sanctuaries, areas in which all waterborne activities are prohibited, typically placed in critical warm-water sites; and (2) manatee refuges, areas where certain waterborne activities (e.g., operation of motorised vessels) are restricted or prohibited. USFWS and FWC use these regulations as key management tools to ensure that adequate protected areas are available throughout Florida to meet manatee habitat requirements with a view toward recovery. Both agencies employ targeted enforcement strategies in an attempt to increase boater compliance with speed zones and, ultimately, to reduce manatee injuries and deaths.

Managers, researchers, and the boating industry have investigated the use of various devices to aid in the reduction of watercraft-related manatee deaths. Propeller guards, for example, would reduce cutting damage associated with propellers, but they are of much less benefit when boats operate at high speeds (e.g., on a plane) because manatees would still be killed by the blunt trauma from impacts of boat hulls, lower units, and other gear (Wright et al. 1995; Milligan and Tennant 1998). There are propeller guard applications, however, that work to prevent sharp trauma by propellers of certain large, slow-moving commercial vessels, such as tugs. Where manatees aggregate in large numbers at or near warm-water refuges, boats are required to move at idle or slow speeds; in these areas, propeller guards are also sometimes used on sight-seeing and tour boats to prevent cutting injuries.

Priority actions related to minimizing manatee injury and death from boat strikes include boater education, enforcement of speed zones and refuges/sanctuaries, maintenance of signs and buoys, compliance assessment, and periodic re-evaluation of the effectiveness of the rules. Such work requires close cooperation between FWC and USFWS managers and law enforcement, county officials, the U.S. Coast Guard, and boaters.

Efforts to Reduce Flood Gate and Navigation Lock Deaths

Entrapment in water-control structures and navigational locks has historically been the second largest cause of human-related manatee deaths. In some cases, manatees appear to have been crushed in closing gates; in others, they have drowned after being pinned against narrow gate openings by water currents rushing through. In Florida, water-control structures and navigation locks are largely operated by State of Florida Water Management Districts and the US Army Corps of Engineers (ACOE); a few structures are operated by private interests.

In the early 1980s, gate-opening procedures were modified to ensure openings were wide enough to allow a manatee to pass through unharmed. Openings and cavities in gate structures where manatees might become trapped were fenced off. Manatee deaths subsequently declined. Much progress has been made since then toward identifying priority water control structures and testing and installing manatee protection devices at those structures. This includes pressure sensor devices, which have been installed at water control structures frequently visited by manatees. An acoustic array that detects the presence of a manatee when it interrupts the sonic signal has been installed on some navigation lock structures. When a manatee is detected near the gate during the last 52 inches of closure, an alarm sounds; the gate stops closing and is then re-opened back to 52 inches. Manatee protection devices (including acoustic arrays, pressure-sensitive piezoelectric strips, grates, and bars) have been installed on all major structures known to crush or entrap manatees. The incidence of deaths in locks and structures is now quite low. An interagency task force continues to monitor structure-related mortality, examine site-specific problems, and make recommendations to protect manatees at water control structures and navigational locks.

Habitat Protection and Restoration

Intensive coastal development throughout Florida poses a long-term threat to the Florida Manatee. Three major approaches have been taken to address this broad problem. First, USFWS, FWC, Georgia Department of Natural Resources (GDNR), and other recovery partners review and comment on applications for federal and state permits for construction projects in manatee habitat areas in order to minimise and mitigate their impacts. Under section 7 of the ESA, USFWS has annually reviewed hundreds of permit applications to the ACOE for construction projects in waters and wetlands that include or are adjacent to important manatee habitat.

A second approach is the development of county manatee protection plans, in coordination with and approval from FWC. The provisions of these plans are implemented through amendments to local growth management plans under the Florida’s Local Government Comprehensive Planning and Land Development Regulation Act of 1985. Manatee protection plans include components on boat facility siting policies, law enforcement, education/outreach, and habitat protection (FWC 2007).

A third approach to habitat protection is acquisition of environmentally sensitive land or conservation easements to limit development and permitted uses on those lands. Both the USFWS and the State of Florida have acquired new areas containing important manatee habitat, adding to federal and state protected area systems. Both the State of Florida and USFWS are continuing cooperative efforts with a view towards establishing a network of important manatee habitats throughout Florida.

As noted above, seagrass as well as freshwater SAV have suffered declines in many regions of Florida. Efforts are underway to improve water quality by reducing nutrient inputs from land-based sources, as well as to remove legacy nutrient loads by dredging muck deposits in some waterways (e.g., IRL). Summarizing these efforts is beyond the scope of this assessment. It is well-recognised, however, that improving water quality is key to successful forage habitat restoration (e.g., planting seagrass or freshwater SAV). A sampling of current manatee habitat restoration projects can be found here: https://myfwc.com/wildlifehabitats/habitat/ahcr/manatee-projects/.

To address concerns about the long-term security of manatee warm-water habitats, efforts have been and continue to be made to protect Florida’s springs and spring runs, where feasible. Many of the springs used by manatees are now in public ownership. Seasonal use restrictions regulate human activities at many, but not all, important sites. Spring flows are supposed to be protected through the State of Florida’s adoption of minimum flow regulations, which (theoretically) would lead to limits on water withdrawals from important spring recharge areas if flows drop below pre-determined thresholds. Minimum flows have been established for most springs important to manatees.

A number of projects have been undertaken to restore springs and spring runs. Some spring runs have been dredged to remove human-caused sedimentation, obstacles have been removed, and banks have been stabilised to minimise erosion. To prepare for the eventual loss of industrial warm-water sites, temporary power plant shutdowns have been closely monitored to evaluate manatee response to these disruptions. When certain key power plant discharges were temporarily eliminated during plant modernisation and repowering, interim heating systems were built and operated by the utility for multiple winters to provide warm water to manatees during cold weather (i.e., ambient water temperatures <16.1° C) (e.g., Reynolds and Scolardi 2016). A passive thermal basin has been created near Port of the Islands in southwest Florida—by digging deep pools that tap into warm, saline groundwater—to replace the pending loss of a nearby warm-water site (Edwards et al. 2021). Managers have finalised a long-term plan that outlines strategies for securing a sufficient warm-water habitat network within each of the four manatee management units (Valade et al. 2020); efforts are underway to implement this plan.

Manatee Rescue, Rehabilitation and Release

Thousands of reports of distressed manatees purportedly in need of assistance have been made to the FWC and other resource protection agencies by a concerned public. While most of the manatees do not require assistance, an average of 108 manatees (min-max = 66–159) have been rescued and treated annually over the past decade (2013–2022) (FWC, unpublished data, https://myfwc.com/research/manatee/rescue-mortality-response/statistics/rescue/yearly). A record 159 manatees were rescued in 2021, with many debilitated due to the loss of seagrass on the east coast. Currently, a network of state and local agencies and private organisations (the Manatee Rescue and Rehabilitation Partnership, or MRP)—with oversight from USFWS—evaluates, rescues, and treats these animals (https://www.manateerescue.org/). Reasons for rescue include: cold stress, injuries incurred from boat strikes, injuries from entanglements in crab trap lines and monofilament fishing line, orphaned animals, red tide poisoning, entrapment in culverts and other structures, starvation or malnutrition, and other natural and man-made factors. Programme veterinarians and staff have developed and refined treatments for these animals and have been remarkably successful in their efforts to rehabilitate them. From 1973 through 2019, more than 2000 manatees were rescued (including some that were assisted and released on site); after successful rehabilitation in oceanaria, 676 manatees have been returned to the wild and naïve animals are tracked for up to a year via satellite-linked telemetry (Adimey et al. 2016; FWC, unpublished data).

Media coverage of manatee rescues and releases helps to educate millions of people about manatees, the life-threatening problems that they face, and actions that can be taken to minimise the effect of anthropogenic activities on this species. In addition, many millions of people have had the opportunity to see manatees up close at oceanaria and to participate in manatee education programmes sponsored by several parks. The publicity and outreach inherent in these programmes lead to substantial public support for efforts to protect and recover manatees in Florida.

Public Education, Awareness, and Support

Government agencies, oceanaria, environmental groups, and power utilities have all contributed to manatee public awareness and education efforts over the past several decades. The public has learned about the biology and status of manatees, urgent conservation issues, and the regulations and measures required to assure their protection through the distribution of brochures, posters, videos, press releases, public service announcements, and other media. Outdoor signs have been produced that provide general manatee information and highlight the problems associated with feeding manatees. Several agencies and organisations provide educator’s guides, posters, and colouring and activity books to teachers in Florida and across the United States. Their staff also give many presentations to schools and citizen groups each year and distribute educational materials at festivals and outreach events. Information on manatee viewing opportunities has also been made available to the public.

Many public awareness materials have been developed specifically focusing on boater education. Waterway signs are produced and distributed alerting boaters to the presence of manatees. Brochures, boat decals, boater’s guides, and other materials with manatee protection tips and boating safety information have been produced and are distributed by law enforcement groups, through marinas, and boating safety classes. Educational kiosks have been designed and installed at marinas, boat ramps, and other waterfront locations. Researchers and managers help to educate law enforcement personnel about manatees and inform them about available outreach materials that can be distributed to user groups. Monofilament fishing line collection sites and clean-up efforts have been established. All such efforts are essential for obtaining public compliance with conservation measures to protect manatees and their habitats.

T. manatus manatus (Antillean Manatee or Greater Caribbean Manatee)

A variety of conservation efforts have been made to protect populations of the Antillean (Greater Caribbean) Manatee, including international agreements, national protections, and actions implemented by local communities and local governments. At the international level, the best-known conservation efforts are integrated into the conventions and protocols ratified by at least 14 countries. Such initiatives include the Convention on International Trade in Endangered Species (CITES) and the Cartagena Convention Protocol Concerning Specially Protected Areas and Wildlife (SPAW). CITES has been in force since 1975, although it has little relevance when the products of exploitation are for domestic consumption. The SPAW Protocol has driven the conservation of the Antillean (Greater Caribbean) Manatee at the regional level. The West Indian Manatee is listed in Appendix I of CITES and, together with the rest of sirenians, is protected by SPAW.

At the national level, several countries have implemented conservation actions, including the creation of protected areas. In fact, all countries of the Caribbean region have designated protected areas in relevant manatee habitats and some of those were created specifically to protect manatees, such as in Belize, Guatemala, Haiti, Honduras, and Mexico. Nicaragua and Costa Rica have a network of protected areas covering over 60% and 85% of manatee habitat, respectively, although in the case of Nicaragua, most of the protected areas are ´paper parks´ (Jimenez-Pérez 2012). In 2004, the Dominican Republic created the Estero Hondo Marine Mammal Sanctuary to protect manatees. Later in 2009, two additional marine sanctuaries were created, Santuario Marino Arrecifes del Sureste and Santuario Marino Arrecifes del Suroeste. In 2013 and 2014, Haiti created protected areas that included manatee habitat: Aire Protégée de Ressources Naturelles Gérées de Port-Salut/Aquin and Aire Protégée de Ressources Naturelles Gérées des Trois Baies.

In most countries, conservation action has not advanced at the same level. Yet Belize, Brazil, Mexico, and Puerto Rico have made significant progress to improve and expand their national protected areas systems. Puerto Rico declared the manatee as its national mammal, calling attention to its protection and conservation (Mignucci-Rodríguez et al. 2019). In Brazil, the new 2018–2032 Blue Initiative includes the creation and consolidation of protected areas, Ramsar Sites, and conservation of threatened species (Maretti et al. 2019). Examples of these efforts include the creation of three protected areas: Arapiranga-Tromai, Itapetininga, and Baía do Tubaráo Extractive Reserves.

Protected areas are a significant tool in the conservation of sirenians (Marsh and Morales-Vela 2012). However, this tool has minimal effect if it does not include adequate enforcement, meaningful involvement of local communities, and well-articulated management plans that outline protected area goals, objectives, and benchmarks. Achieving this type of management integration has been challenging in developing countries. Due to poor socioeconomic conditions, manatee conservation is often not a high priority. Economic and political pressure exists for the continuation and expansion of commercial activities---such as fishing, logging, tourism, and coastal development---known to negatively impact manatees and their habitats (UNEP 2010).

Ideally, manatee conservation strategies need to be associated with building of community support and strengthening local capacity and alternative livelihoods (Aragones et al. 2012; Marsh and Morales-Vela 2012), accompanied by an effective public education/awareness campaign (UNEP 2010), known as community outreach (Mignucci-Rodríguez et al. 2019). Long-term work with local communities can produce multiple benefits for the conservation process (Aragones et al. 2012). These efforts can be strong enough to stop or control manatee poaching, as has occurred in the Sinu River Basin and Ciénaga Paredes in Colombia (Castelblanco Martínez et al. 2015) and the Alvarado lagoon system, Mexico. Long-term work with local communities needs to improve in Venezuela, Nicaragua, Haiti, and other parts of Colombia to stop manatee poaching.

Belize, Brazil, Colombia, Costa Rica, Mexico, Puerto Rico, and other countries have a long history of developing programmes that foster community capacity-building, associated with the protection of priority conservation areas and species. The Dominican Republic's Ministry of Education and local non-governmental organisations have made a remarkable effort in public education and awareness of manatee conservation issues (Dominguez Tejo 2016). In some countries, conservation activities, such as the Manatee Day or adopt-a-manatee programmes, are held to raise public awareness. In Mexico, the 7th of September was declared as the National Manatee Day; every year, members of the National Manatee Committee conduct education and awareness activities on that day. The Dominican Republic also has a Manatee Day Celebration at the national level (Dominguez Tejo 2016). Puerto Rico declared 7 September as the “Day for the Conservation of the Caribbean Manatee in Puerto Rico,” with the Caribbean Manatee Conservation Center leading community outreach activities and public awareness (Mignucci-Rodríguez et al. 2019).

Habitat connectivity is important for manatee conservation because their movements can cover long distances of at least 245 km (Morales-Vela and Padilla-Saldivar 2009, Castelblanco-Martinez et al. 2013, Deutsch et al. 2022a). This connectivity is critical, particularly between protected and unprotected areas, as well as in the transboundary areas of neighbouring countries that share manatee habitats (Morales-Vela and Bahena-Basave 2023). However, habitat fragmentation must be assessed with a comprehensive vision that includes the human dimension. Some regional conservation studies have been conducted to better understand the habitat connectivity and transboundary movements of manatees (e.g., between Mexico and Belize), but these are not multidisciplinary and more research is needed. Stakeholders may need to accept that there is an inherent social dimension in any conservation effort for manatees (Aragones et al. 2012, Hines 2012, Hines et al. 2012, Marsh and Morales-Vela 2012). Therefore, it is urgent to prioritise coordinated and multidisciplinary efforts between neighbouring countries to strengthen integrated ecosystem assessments and management, considering the human dimensions.

Several countries have developed national recovery plans for manatees, including Belize, Colombia, Costa Rica, Guatemala, Jamaica, Mexico, Puerto Rico, and Venezuela. However, with the exception of Mexico, many of the existing plans have never been updated. According to international planning standards, recovery plans should be updated at least every five years to reflect changes in available information, agency leadership, the status of threats, progress toward implementation, and other aspects. Recovery plans should include criteria for determining the status of the species and for assessing progress in reaching recovery goals and objectives (UNEP 2010). Countries that still do not have a plan need to develop one and tailor it to their specific needs and conditions. Recovery plans should be based on the best available data and include an annotated and prioritised list of the activities to be adopted in the fields of conservation, scientific research, law enforcement, and education, among others.

Country-specific conservation recommendations were provided by the Regional Management Plan for the West Indian Manatee (UNEP 2010). However, most of those recommendations remain unaddressed; therefore, their adoption and implementation is strongly recommended, when possible. As conditions change, it is also necessary to update the plan. For example, research studies must be implemented to assess the manatee population and distribution. There is no current information on the status of manatee populations in Guyana, Trinidad and Tobago, Nicaragua, Surinam, and Venezuela. In areas with little or no information, standardised surveys should be conducted in areas of past and present manatee distribution to better inform an assessment of the subspecies' status. Threats must be identified, monitored, and prioritised to establish appropriate management and regulatory measures. These surveys and assessments will provide crucial information on the health and structure of local manatee populations within countries. This is particularly important in areas in which coastal waters are polluted by the inappropriate disposal of wastewaters from urban centres, agriculture, and the mining industry.

Stranding networks and rehabilitation centres are other valuable conservation tools. Manatee strandings provide scientists with a means to obtain biological information, which otherwise is difficult to obtain from studies of manatees in the wild. However, few countries have marine mammal stranding networks or facilities to take care of live stranded animals. These include Brazil, Belize, Dominican Republic, Colombia, Mexico, and Puerto Rico (Adimey et al. 2012). Brazil has made major achievements in this field, with 142 manatees released over 29 years of rescue and rehabilitation (Belensiefer et al. 2017). In Belize, the Wildtrack facility handles manatee rescues and, since its creation in 1999, they have rescued 28 manatees and released 14 to the wild (P. Walker pers. comm. 2021). In the Dominican Republic, the manatee stranding network is supported by the Center for Rescue and Rehabilitation of Aquatic Species at the National Aquarium (Dominguez Tejo 2016). In Colombia, rescue and rehabilitation are coordinated by the Fundación Omacha and, to date, they have rescued several manatees and returned them to the wild. In Mexico, there are 10 facilities equipped to care for manatees, located in Veracruz, Tabasco, Chiapas, and Quintana Roo (Ortega-Argueta and Castelblanco 2020; 41 manatees are under care, 15 of them having been born in captivity as of 2021. In Brazil, six facilities handle manatee rescue and rehabilitation.

The Caribbean Manatee Conservation Center in Puerto Rico has the strongest, fully dedicated manatee rehabilitation programme that includes adequate facilities, a veterinarian, and biologists that handle manatee rescue, short-term medical emergencies, and long-term rehabilitation (Mignucci-Giannoni et al. 2011). The centre has handled over 52 cases of live-stranded manatees in Puerto Rico and the Virgin Islands. Of these, 16 have been returned to the wild. The centre has also assisted with Caribbean Manatee rescue and rehabilitation in other countries, such as Cuba, Colombia, Haiti, Guyana, Turks and Caicos, Panama, and Venezuela (A. Mignucci-Giannoni pers. comm. 2021).

Other facilities exist in the Americas, Europe, and Asia that hold Antillean (Greater Caribbean) Manatees under long-term human care. These include facilities in Denmark (1 manatee), France (2), Germany (1), Guyana (2), Italy (1), Japan (2), Mexico (9), Netherlands (1), Poland (1), Singapore (1), Spain (1), and Venezuela (2). To date, over 180 manatees of this subspecies are under human care.