The species is threatened by multiple human activities throughout its range, destruction of riparian habitat, overfishing, contamination of water bodies—especially by gold mining, fossil fuel exploration, and the use of pesticides and fertilizers, diseases spread by domestic animals, and mismanaged tourism (Duplaix 1980, Schenck 1999, Utreras and Tirira 2011). Human populations are increasing and expanding. In the last census, the Amazon region registered the highest population growth in Brazil. Illegal settlements, road opening and deforestation threaten pristine habitats. Colonization of new areas are expected, followed by intensive exploitation of natural resources. Furthermore, proposed mega-projects in the 2007 Brazilian Growth Acceleration Plan represent a significant threat to Brazilian Amazonian and Pantanal habitats. Changes in government and environmental protection policies in Brazil endanger the pristine areas of the Amazon, Pantanal and Cerrado. Between 2017 and 2019 4,500 km² of the Amazon were lost due to deforestation and burning, of which 65% occurred in 2019 (Cannon 2019, https://news.mongabay.com/2019/11/deforestation-preceded-fires-in-massive-area-of-amazon-in-2019/). From August to November of 2019, at least 1.5 million hectares of Brazilian Pantanal were burned (https://www.dw.com/en/brazils-next-fire-disaster-in-the-pantanal-wetlands/a-51199164).
Hunting for the pelt trade was the greatest threat to the Giant Otter in the past and the species came close to extinction in the early 1970s in Ecuador, Colombia, Venezuela, Bolivia, and Brazilian Pantanal (Duplaix 1980). From 1960 to 1969, records indicated a regional harvest of 12,390 giant otter skins. In 1973, giant otters were placed on CITES Appendix I, and the enforcement of international trade restrictions on Giant Otter skins in 1975 finally ended Giant Otter hunting (Recharte and Bodmer 2010).
The Giant Otter remains endangered because of the low recuperation rate of relict populations now also under pressure from human activities (Groenendijk et al. 2015). Direct conflict between humans and otters is an increasing problem. Otters may be killed for fun or out of fear, or, more often, because they are seen as competitors for fish by loggers, miners, and fishermen, who often blame them for depleting fish resources used for local and commercial consumption (Gómez and Jorgensen 1999, Recharte et al. 2008, Rosas-Ribeiro et al. 2012, Utreras and Tirira 2011). Giant Otters can drown in fishing nets and traps and are also blamed for damaging them (Rosas-Ribeiro et al. 2012, Utreras et al. 2013). Fish farming is rapidly increasing in the species’ range, for example in parts of the Ecuadorian Amazon, and expose otters to retaliation killing (V. Utreras pers. obs.). Cubs are sometimes captured illegally to be kept as pets (M. Marmontel pers. obs).
Giant Otters are highly susceptible to persecution: they are large, conspicuous, social, and very vocal. They are active at daytime and occupy open habitats and stable territories. Their signs—latrines and dens—are easily recognizable, making it possible to identify areas of recent activity by a group (Groenendijk et al. 2005). Individuals and groups often react to people by approaching to investigate. Moreover, only the dominant pair produces young, and usually only once a year. During the pelt trade years, these life history attributes made them an easy target for fishermen. In 2017, a Giant Otter group was killed by fishermen in the Pantanal and according to locals, kills occur frequently during the fishing season (C. Leuchtenberger pers. obs.). In 2011–2012, the Kanamari indigenous people promoted a massive Giant Otter killing in their territory (Território Indígena Kanamari), based on their perception that the species was overfishing the river turtle population. The community leader bought 300 cartridges for the hunters, who shot 64 Giant Otters (Endo pers. comm. 2012). Such incidents of targeted killing can lead to extinction of small populations in a watershed.
Gold mining, artisanal as well as industrial, is a significant threat to the species, particularly in the Guiana Shield region, in southeastern Peru, the western region of the Ecuadorian Amazon, and northern Pantanal. The main impacts are habitat destruction, sedimentation of rivers, and pollution (Kimbrough 2014). Gold miners cut swathes into the floodplain forest and blast river banks with pressure hoses, using mercury to amalgamate gold particles. Gold prices are at a record high, whereas mercury is inexpensive. Forest conversion to mining increased six-fold from 2003–2006 to 2006–2009 (Swenson et al. 2011). Even a decade after mining stopped, areas affected still had depleted fish populations and had not been re-colonized by otters. In areas of gold mining, fish are contaminated with mercury. Gutleb et al. (1997) found that mercury concentrations in the majority of fish near Manu National Park were higher than considered tolerable for the Eurasian otter. Migration of contaminated fish and long-range atmospheric transport of mercury probably increase the area of influence of such contaminants. Contamination of otters by other heavy metals through pesticides and other agrochemicals is still poorly understood.
The many planned hydroelectric dams in the species’ range are a major threat to Giant Otters. These will alter hydrological regimes of rivers and affect fish populations and habitat (Latrubesse et al. 2017). Dams disrupt the annual cycles of inundations, vital for the maintenance of populations of flood dependent species such as the Giant Otter (Mourão et al. 2010, Alho and Sabino 2011). One hundred and eighty-four new dams are planned or under construction, greater than two MW capacity over the next 20 years in the Amazon. These dams would include five of the six major Andean tributaries of the Amazon. Sixty per cent of the dams would cause the first major break in connectivity between protected Andean headwaters and the lowland Amazon. Giant Otters are able to live in some artificial lakes, such as the shallow Balbina Reservoir in Brazil (Rosas et al. 2007). In other areas, hydroelectric dams have depleted Giant Otter populations, as did the Curuá-Una Hydroelectric in the Brazilian Amazonia (Rosas et al. 2007). Around the Pantanal, there are over 115 projects of small hydroelectric plants. Other major infrastructure projects include the Inter-oceanic highway in southeastern Peru, and the Initiative for the Integration of the Regional Infrastructure of South America (V. Utreras pers. comm. 2012).
Giant Otters are vulnerable to disturbance from poorly managed tourism, including sport fishing. It is important to control increasing levels of tourism on lakes and rivers both in and outside protected areas (Groenendijk and Hajek 2006). Research has shown that Giant Otter reproductive success and sighting success by tourists is considerably lower on unmanaged lakes than on managed lakes (Groenendijk and Hajek 2006).
Giant Otter cubs held in captivity have died of canine parvovirus, and all mustelids are susceptible to canine distemper, so domestic animal diseases may pose a serious threat to wild Giant Otter populations. Infection can also occur in remote areas, since transient otters and people hunting with dogs travel large distances with potential for contact and infection of vulnerable otter populations (Schenck et al. 1999).
Climatic changes are predicted to increase suitable areas for Giant Otters (Cianfrani
et al. 2018). However, long-term habitat and climatic modifications will increase the exposure of suitable core otter areas to the negative effects of the surrounding unsuitable areas (Cianfrani
et al. 2018). The species also has a high specialized niche, making it more vulnerable to climate change.
