The 2008 Red List Assessment described the Common Hippopotamus (Hippopotamus amphibius) populations as Vulnerable, as the population experienced considerable declines in the mid 1990s and early 2000s. The most recent population estimates suggest that, over the 8 years since the last assessment, Common Hippo populations have largely remained stable. The 2008 Red List Assessment estimated Hippo populations to be approximately 125,000 and 148,000, with half of the 29 countries in which Common Hippos were found reporting declines. Our current assessment yields a lower population estimate, on the order of 115,000-130,000 Hippos. However, we believe that the observed downward shift in total population size likely reflects overestimated population sizes from some countries in the 2008 Red List Assessment that have now been corrected. Because of this, a change in the Risk Category classification of Common Hippos is not warranted at this time. The conservation status of Hippos remains precarious and the need for direct conservation action to protect Hippos and Hippo habitat across their range is a priority. Although in some countries Hippo populations have stabilized, Hippo population declines are still reported in many countries. The growing and unabated threats of habitat loss and unregulated hunting are major challenges to Hippo population viability and persistence.

Common Hippopotamus (referred to as Common Hippos or Hippos hereafter) are found in many countries throughout sub-Saharan Africa in suitable wetland habitats. The species still occupies much of its former range from 1959, although population sizes have declined. Common Hippos occur in rivers throughout the savanna zone of Africa, and main rivers of forest zone in Central Africa, in Angola, Benin, Botswana, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, Côte d’Ivoire, Democratic Republic of Congo, Ethiopia, Equatorial Guinea, Gabon, Gambia, Ghana, Guinea, Guinea Bissau, Kenya, Rwanda, Senegal, Sierra Leone, Somalia, Sudan, South Sudan, Swaziland, Malawi, Mozambique, Namibia, Niger, Nigeria, Republic of Congo, Sierra Leone, South Africa, Tanzania, Togo, Uganda, Zambia, and Zimbabwe.

Common Hippos were already rare in Egypt by the time of the Renaissance. From the end of the Roman Empire up until towards 1700 at the latest, the Hippo was still present in two well disjunct zones in the Nile Delta and in the upper Nile. Through the 1700s, records become increasingly scarce, and the latest definite records are from the early 1800s (Manlius 2000).

Our current assessment suggests that across their range, there are on the order of 115,000-130,000 Common Hippos extant today. There are clear regional differences in population size and distribution across the range. Eastern and Southern African countries represent the conservation stronghold for this species and are the regions where the largest numbers of Common Hippos occur. Although Common Hippos are found in many West African nations, overall population sizes tend to be much smaller, either because of less available habitat or the higher density of human populations. Existing genetic research has suggested putative subpopulation designations among the regions (Okello et al. 2005, Stoffel et al. 2015) and future research on this is needed.

Western Africa
The species is less widely distributed and typically occurs at low densities in West Africa. Common Hippos in West Africa are absent from the rain forests except near large rivers. They are most abundant in estuarine habitats and on the lower reaches of rivers. Current data suggests that Hippo populations in this region are at the highest level of risk due to the fragmented nature of their distribution and the high frequency of Hippo-human conflicts. Common Hippo population in this region is estimated to be approximately 7,500 spread over 19 countries. Within the region, Common Hippos are most abundant in Cameroon and Burkino Faso.

In Côte d’Ivoire, Hippos are still present in Nzo Reserve, Mont Sangbe National Park, Haut Bandama and maybe Marahoue. Scattered small populations still remain in the lower parts of Sassandra, Bandama and Comoe Rivers (Roth et al. 2004). The largest populations in the country are found in Comoe National Park, with a total population over 100. Large numbers of Hippos were reportedly killed during recent civil unrest, up to 2012, with abundant hippo bones still evident. The estimate for Côte d’Ivoire puts the Hippo population at 500.

No formal country-level Hippo census has been conducted recently in Ghana. Hippos are thought to reside in Bui, Digya and Mole National Park, with Bui National Park as the most populated, supporting hundreds of Hippos at one point. Recent hydroelectric development in this area may have comprised this population.  A well-monitored population of Hippos also reside in Wechiau Community Hippo Sanctuary (Sheppard et al. 2010). The current Hippo population in Ghana is likely 150-200 individuals.

Extremely limited population information is available for Hippos in Togo. Keran National Park, Togodo Game Reserve and Nangbeto Lake are reported to have resident Hippo population but recent counts have not been reported. Rough estimates for Togo put the population at 200-500.

In Benin, the largest number of Hippos reside in the Mono River Basin, in small, isolated groups and larger aggregations, and in Pendjari National Park in the north, with an estimated 100 and 350 Hippos respectively  (Amoussou et al. 2006). In Benin, Hippos are also likely to be found in the Oueme, Niger River and Sota Rivers. Annual census counts are conducted in Pendjari National Park and support a country-wide estimate of 500.

Burkina Faso has a number of large protected areas where Hippos reside, including “W” National Park which extends into Niger, and Benin,  Arly and Deux Bales Forest reserves, Bala Biological Reserve (Dibloni et al. 2010, 2012). Hippo have also been reported in Soula, Bagre, Tengrela and Sikorola Banzon Lakes, Comoé-Léraba, Sourou, and Bougouriba Rivers. Estimates for Hippos in Burkina Faso suggest 1,500-2,000 Hippos.

Although small in area, Guinea Bissau is thought to support a substantial Common Hippo population, particularly on the islands of the Bijagos Archipelago and along the numerous inland rivers. Local scientist estimate 100 Hippos based on behavioural research in the Orango complex, Bijagos Islands. Corubal River and Rio Cacheu National Park are also reported to have resident Hippo populations.  The estimate of Hippos in Guinea Bissau is roughly between 200-500 individuals.

The species is also found on many of the rivers in Guinea. Haut Niger National Park has been estimated to have the largest Hippo population in Guinea (Brugiere et al. 2006) with around 100 individuals in the wet season. Badiar National Park and Niger River also have resident Hippos. Guinea may have a Hippo population on the order of 500 individuals.

Senegal has been reported to have a similar sized population (approximately 500 individuals) with the majority of Hippos found in Niokolo-Koba National Park, with widespread reports of hippo crop-raiding.

Low density and isolated Hippo populations are also found in the Gambia in Gambia River National Park, likely home to about 40 animals.
In Mali, approximately 100 Hippos are reported to reside in Boucle du Baoule National Park.

Sierra Leone has an estimated 150 Hippo across several protected areas including Tiwai Island Wildlife Sanctuary, Gola Rainforest National Park and Loma Mountains Forest Reserve. Hippos may also be present in Outamba-Killmi National Park and Kambui Hills South Forest Reserve.

Hippos are reported to reside in one national park in Equatorial Guinea in Monte Alen National Park. There are likely 50-100 Hippos there.

In Gabon, Hippos are reported to reside in Wonga-Wongue National Park, Sette-Cama and Moukalaba Forest Reserves. They have also been recently surveyed in the Gamba Complex (Reitmann 2012), a network of protected areas in south-western Gabon which includes Moukalaba-Doudou National Park and a series of lagoons, lakes and rivers. Based on this information, there are an estimated 250 Hippos in Gabon.

Another important regional stronghold for Common Hippos is Cameroon and recent census information has been collected in many parts of the country (Scholte and Iyah 2016). The larger populations of Hippos have been reported in Benoue, Kalamaloue, and Faro National Parks.  Faro National Park has the largest numbers, with a 2016 census estimating nearly 1,000 individuals. Hippos have also been reported in Lakes Lagdo, Maga, Fianga, and Mbam et Djerem National Parks. The current estimates for Cameroon suggests a country-wide Hippo population of 1,500-2,000.

In Niger, 150-200 Hippos are reported to reside in W National Park , the Tapoa and Mekrou Rivers and along the Niger.

No recent census information is available for Nigeria, although Hippos have been reported in low numbers across a number of locations including Kainji Lake and Okumu National Parks, and Kwiambana, Sambisa and Yankari Game Reserves, and Hippos may still occur in the Niger Delta. An estimate 100 Hippos remain in Nigeria.

The majority of Hippos in Chad are reported to occur in Lake Chad and the Chari River including Mandelia and Manda National Parks. They are rarely found in Bahr Salamat, a river that crosses Zakouma National Park and  Salamat Wildlife Game Reserve, but they inhabit Lake Iro in the latter. Hippos are no longer present in Lake Fitri. Restricted distirbutions of Hippos have been reported  in Binder Leré Faunal Reserve (Brugiere and Scholte 2012). In some areas, Hippos are locally abundant and damage to crops and human casualties are increasing (Malachie Dolmia pers. comm.) . The current estimates for Chad suggests a country-wide Hippo population of 500.

Limited information is available on Hippos in Central African Republic (CAR), but Hippos are reported from a number of national parks and forest reserves at low densities. The best estimates are available for the Chinko protected area which is thought to be home to 200 Hippos. According to local experts, Hippos are still found around villages in eastern CAR where they hide in major rivers like Mbari but enter into rice fields where they are regarded as pest and crop raid. Hippos still  likely reside in low numbers in Andre Felix, Bamimgui-Bangoran  and Manovo-Gounda-Saint Floris National Parks and a number of forest reserves (Yata-Ngaya, Gribingui, Koukourou, Dzanga-Sangha). Country estimates put the population at 200-500 individuals.

No formal counts have been made in the Congo recently, but the species presence was confirmed in  Odzala and Conkouati-Douili National Parks, and the Nyanga Nord, Lefini and Tsoulous  Forest Reserves. Local experts put the Congo Hippo population at 50 individuals.

Eastern Africa
Historically East Africa has been home to the largest populations of Common Hippos and despite some dramatic declines in particular countries in this region, populations number in the tens of thousands regionally, with an estimated total for Eastern Africa as a whole at about 50,000. Regionally, the largest populations of Common Hippos are found in Tanzania.

In Sudan, Hippos previously have been reported in Dinder National Park, however the current population size or status there is unknown.

In South Sudan, no recent Hippo censuses have been conducted, however, Hippos are reported in several areas. Most Hippo populations in the country are on the White Nile river except those in Southern National Parks (rivers Tonj and Sue) and Boma National Park and some other isolated small populations in North-western South Sudan.  The largest aggregation of Common Hippos in South Sudan is reported to be in Nimule National Park,with an estimated population size of 2,000, but Hippos also occur in Badingilo National Park (including former Mongalla Game Reserve), in Zeraf and Shambe National Parks, Juba Game Reserve and Fanykang Game Reserves (Markéta Antonínová pers. comm). Common Hippos populations are reported to be declining and the regulation of hunting is limited due to military actions in this country. A rough estimate for South Sudan puts current Hippo populations at approximately 2,500.

Recent estimates from Ethiopia suggest that Hippos occur from the Djibouti border through the highlands  to the south and south west, with the main threat reported to be habitat loss, degradation, and unregulated hunting. Earlier Hippo census efforts  found the main strongholds to be the Omo, Awash and Great Abbi (Blue Nile), Gibe Rivers. Hippos are also found in many of the larger lakes (Lake Abaya, Lake Hawassa, Lake Langano, Lake Ziway, Lake Chamo) and isolated populations in smaller swamps and pools. The northern limit of the species is the Setit River. One of largest hippo populations are found in Dhati-Welel National Park, a newly gazetted area in May 2012. Very few animals remain in neighbouring Somalia (ca. 50) although some small groups have been reported on the lower Shebeli River and along the Juba River. No common hippos have been reported from Djibouti. Current estimates for Ethiopia are 2,500.

Although hippos were found in Eritrea in the mid 1960s and 70s, it is likely they are no longer present in the country.

The species occurs in a number of reserves and parks throughout Kenya. The most recent census information is available for the Masai Mara National Reserve (4,200, Kanga et al. 2011). Other locations where Hippos have been reported, but not recently confirmed, in Kenya include Amboseli , Lake Nakuru, Meru, Nairobi, and Tsavo National Parks and several National Reserves  - Buffalo Springs, Kora, Lake Bogoria, Mwea, North Kitui and Samburu. Hippos are also found in Lake Victoria. Although recent censuses are not available, best estimates for Kenya put the Hippo population at 6,500 for the country.

In Tanzania, the most recent census information are from 2001 (TAWIRI 2001). In September 2001 (dry season), a total of approximately 20,000 Hippos were counted with the largest concentrations of Hippos observed in Kilombero, Rufiji and Great Ruaha Rivers. Although this direct census likely presented an underestimate because of uncounted or undetected animals, we use this value because the census effort is not current. The census effort found that a large proportion of Hippos (80%) counted were found inside protected areas, highlighting the importance of the the protected area networks to Hippos in Tanzania. Most Hippos were found in southern Tanzania and especially in the Selous Game Reserve and its immediate vicinity. Other important localities for Hippos were the Katavi-Rukwa protected area complex. The Ugalla and Malagarassi Rivers and the Serengeti and Mara Rivers.
Lack of Hippo population information in Uganda is surprising given the historical prevalence of Hippo populations and Hippo research in this country. The principal concentrations of the species in Uganda in the past were in two large national parks, Murchison Falls and Queen Elizabeth. At one time the population in Queen Elizabeth National Park (QENP) reached 21,000, but this was reduced to about 14,000 in a culling programme of the 1950s. Counts in the early 1970s returned about 11,000 but heavy poaching during the Amin years had left only a couple of thousand by 1989 when 2,172 were estimated from an aerial sample count. Since then, Hippo populations  have recovered. Current estimate for QENP are from 5,000 to 6,000 Hippos (Andrew Plumpter pers. comm). In addition, Hippos inhabit several other national parks and wildlife reserves as Kibale National Park, Katonga and Kabwoya, East Madi Wildlife Reserves, and Lake Mburo National Park as well as Semliki River and Lakes Victoria and Kyoga. Most Hippo populations in Uganda are reported as stable or slightly increasing. The overall estimate for the country is 10,000 individuals.

Common Hippos have a wide distribution in DR Congo including some in the north-west of the country although the bulk is in the east, where they occur around Epulu and Wamba and along some of the larger rivers in the Ituri Forest. Other populations occur on the Zaire River (Yangabi), Bomu River, Rusizi River and elsewhere in several national parks including Garamba, Kundelungu, Salonga, Upemba and Virunga as well as Luama Hunting Reserve. At one point in the mid 1980s, there was an estimated 26,000 Hippos across the country. However, these numbers declined dramatically in the 1990s and early 2000s as a function of widespread civil unrest and associated rampant unregulated hunting. The most dramatic declines were observed in the Virunga National Park. Since 2002, Hippo population have increased slightly in most protected areas as reported for Garamba National Park where 2,600 Hippos in main rivers – Aka, Dungu, Garamba - and the neighbouring hunting areas were counted (Schapira and Antonínová 2011). Estimates from a 2014 UNESCO mission in Virunga area reported 1,500 hippos with current estimates  at 2,000 individuals (Deo Kujirakwinja pers. comm). This suggests current country-wide estimates for DR Congo are likely approximately 5,000.

Census information is available for Rwanda as an aerial survey in Rwanda, conducted in 2013, found some 800-1,000 Hippos in Akagera National Park (MacPherson 2013), which has historically been an area where hippos have been abundant. Their distribution is widespread along the wetland fringes with focal points in Lakes Rwanyakizinga and Hago.

Common Hippos in Burundi have been reported on the Malagarazi, Ruvubu and Rusizi Rivers but there are conflicting reports over numbers. The largest populations appear to be in Rusizi Reserve, with an estimated population of 500 Hippos. Both earlier and current reports suggest that unregulated hunting is widespread. The estimated Hippo populations in Rwanda is 1,000 Hippos and 750 in Burundi.
 
Southern Africa
Southern Africa is also home to large populations of Common Hippos. This region has also experienced Hippo population declines related to civil unrest and war. The coarse estimate for the region is 60,000. Regionally, the largest populations of Common Hippos are found in Zambia.

Zambia has historically been a stronghold for Common Hippo populations and recent country-wide estimates suggests Zambia continues to serve as a stronghold for the species. The population is widely distributed, with the key Hippo areas in order of importance based on population size as Luangwa River (25,000), Zambezi River (6,500), Kafue River (4,000) and the Lufupa River tributary of Kafue River (1,600). The Luangwa, Zambezi and Kafue Rivers hold 87 % of the Hippo population in Zambia. As with Hippo populations in other countries, the Hippo populations in Zambia fluctuates in response  to changing rainfall conditions and available forage (Chomba 2013). The densities of Hippos range across these areas with densities highest in the Luangwa River reaching as high as 42 Hippos/per km of river stretch in some areas. Generally the national population is stable, although there is concern of Hippo viability particularly outside protected areas where human settlements and fishing activities have increased leading to increased human-Hippo conflicts from crop raiding or Hippo attacks.

Malawi also has areas densely populated with Hippos with most populations confined to national parks and other protected area. The largest and potentially increasing population of more than 2,000 individuals inhabits Liwonde National Park. More than 300 Hippos were reported in Vwaza Marshes National Park, with smaller populations in Majete and Kasungu National Parks of no more than 100 individuals. All these popualtions are stable or increasing. Hippos disapeared from Nkhotakota Wildlife Reserve, although the suitable habitat remains there (Samuel Kamoto, Craig Raid, Craig Hay, Patricio Ndadzela pers. comm.). Dozens of individuals persist in Lake Malawi and the shire rivers (Johnathan Vaughan pers. comm.), areas where Hippos had been previously abundant. Whereas the conservation  in protected areas is good, in other areas, hippos are illegally hunted for bushmeat and teeth. The total population estimate for Malawi is 3,000.

In Zimbabwe, Common Hippos are found in areas that border the Zambesi river in the north and the Limpopo river in the south. Hippos are also found on privately owned game farms, conservancies, recreational lands and other unprotected areas throughout the country.  As a result of intensive agricultural development, Zimbabwe has more than 50,000 small to medium-sized dams which could provide habitat for hippos. The most recent population information on Common Hippos in Zimbabwe is from 2007-2010 (Zisadra et al. 2010) and suggests that Zimbabwe’s Hippo population is stable at approximately 5,000 individuals.

In 1986, Mozambique was thought to have an estimated population of approximately 20,000 Common Hippos. However more recent surveys have found this estimated population to be a gross overestimation (Mackie et al. 2013). Populations of Common Hippos were surveyed in 2010 during a national crocodile survey (and corrected to account for under-counting). Unregulated hunting and poaching of Hippo has drastically reduced Common Hippo numbers and the trend continues (Anderson and Pariela 2005). In 2013, the CITES Standing Committee suspended all Hippo trade or export from Mozambique due to the lack of information on the abundance, distribution and hunting permits of Hippos in the country. There are now estimated to be approximately 3,000 Hippos in Mozambique with the majority of the Hippos found in Lake Cabora Bassa and the Zambesi river. Other areas with sizeable Hippo populations included the Niassa National Reserve, Maputo River and Reserve, and Save, Pungwe and Ruvuma Rivers.

In the 1960s, Hippos were reported as widespread in Angola. There is limited information on current distribution and population sizes. Hippos have been reported to occur in Cunene, Cubango, Cuando, Cuanza, Cuvo, Longa and Zambesi rivers, in Bicuar, Cameia, Mupa, and Quiçama National Parks and in Luando Game Reserve. The population numbers in Quiçama NP and Luando GR are estimated as less than 30 and 100 individuals, respectively. The main threat to Hippos in Angola is poaching and human develepoment along the rivers (Pedro Vaz Pinto pers. comm.).  Although no census information is available, based on this information, an estimated 500 Hippos likely remain in Angola.

Hippo abundance and distribution in Namibia is based on recent censuses by the Wildlife Research and Monitoring, Ministry of Environment & Tourism, and puts the population at approximately 3,300. Namibia supports Common Hippos largely  in two areas: Okavango, including Bwabwata National Park, and Kwando, where the majority of Hippos are found, including Bwabwata National Park, Mudumu National Park and Nkasa Rupara National Park.  Some Common Hippos can also be found in the Linyanti, Chobe and Zambesi Rivers.

Hippos in Botswana are centred in the Okavango Delta and also in the Chobe, Linyati River systems. Outside this area, a small population may still exist near Ghanzi although some observers think this is unlikely. The most recent estimated total for northern Botswana where Hippos reside is 1,600 in the wet season and 500 in the dry.

South Africa has country-wide information on Common Hippos  as a national assessment for the species has recently been completed (National Red List Assessment in review). There are two major subpopulations in South Africa, occurring in the lowveld of north-eastern South Africa and that of northern Kwa-Zulu Natal. Most other populations across the country are fragmented by fences or other barriers that limit movement. Water quality and quantity has declined, which has possibly led to fragmentation too. Kruger National Park is believed to be home  to 3,000 individuals, which represents an increase for the park. The current Hippo population in Mpumalanga is estimated at 1,000 animals, where 575 animals occur in provincial and private nature reserves, with an estimated 430 Hippos in the neighbouring river systems. Most of the hippo subpopulation in the protected areas and rivers close to the KNP show strong positive growth trends, in spite of significant Hippo removals through damage-causing animal complaints and pro-active Hippo capture operations In Limpopo, there is an estimated 700 animals, with another 700 residing in the Olifants and Letaba Rivers. Hippo in KwaZulu-Natal are mainly confined to the large rivers, coastal lakes and estuaries of north eastern Zululand and Maputaland regions of the province.  Recent population estimates for the province of KZN suggests approximately 2,000 animals in 10 formally protected areas and on 22 private and communal protected areas. Currently the largest single populations are found in the St Lucia Game Reserve component of the iSimangaliso Wetland Park (1,000 individuals) and Ndumo Game Reserve (200 individuals). In the North-West Province, there are approximately 100 individuals on formally protected areas and on private lands. In Swaziland, the population is currently estimated at about 120 animals. These estimates suggest that there are 7,000 Common Hippos in South Africa.

As its name suggests, the Common Hippopotamus is an amphibious creature, which spends the day in water and emerges at night to feed. The Hippopotamus uses the water only as a retreat and typically does not eat aquatic vegetation, rather they forage on grass at varying distances from a water source. Hippos rely on a range of water sources – rivers, lakes, and wetlands although seasonally the animal can survive in muddy wallows.  Hippos require some form of permanent water particularly in the dry season as their skin must remain moist and will crack if exposed to the air for long periods. The skin physiology is complex and not fully understood but is clearly adapted for an amphibious existence. Hippos secrete a red liquid from subdermal glands which is thought to function as both a sunscreen and antibiotic (Saikawa et al. 2004).

Common Hippos are gregarious, social, polygymous animals when resting in water by day, with herd sizes ranging from the tens to a hundred. The social habits of the species have been studied by Klingel (1991), who found that the "schools" are groups of females and juveniles. The social system is based on mating territoriality. Females become sexually mature between the ages of 7–9, and males 9–11. Females typically bear a single offspring every other year as lactation can extend for 18 months or longer. In captivity, reproductive activity and sexual maturity occurs in younger individuals. Territorial males monopolize a length of the shoreline of the river or lake but tolerate bachelors within the territory provided they behave submissively. Non-breeding males also settle outside territorial areas, especially seasonal wallows. Fights for the possession of a territory can be fierce and the animals may inflict considerable damage on each other with their huge canines but minor conflicts are usually settled by threat displays, of which the "yawn" is the most conspicuous. Territorial males do not normally fight each other and severe fights usually occur only when a bachelor challenges a territorial male for control of its territory. There is little association between animals when they are feeding at night, except between females and their dependent young, and the males do not then behave in a territorial fashion.

The male Common Hippo, rarely the female, spreads its dung by wagging its tail vigorously while defecating, both in the water and on land, where it is thought to have a signalling rather than a territorial function. The dung piles may serve to orient Hippos or may mark territories.

Vocalizations take the form of complex bellows and grunts, which presumably have a signalling function. Sounds may be made either on land or in the water and may be transmitted simultaneously through air and water. This is the only known case of amphibious calls in a mammal.

It is likely that thermoregulation has determined the nocturnal feeding habits of the animal. Hippos typically leave wallow or pool soon after sunset and spend night hours grazing on short grass swards for up to several kilometres from water. The distance animals travel to grazing areas likely varies seasonally and among different areas. Grazing areas, which are kept short by the activities of the Hippopotamus, are often referred to as Hippo lawns. Although Hippos can graze every night, there are usually animals present in the water all night, as some return after a few hours and others leave later. Mothers with very young calves represent the only apparent social structure at grazing areas  as there is no clear organization at the grazing lawn.The animal feeds by plucking the grass with its wide, muscular lips and passing it to the back of the mouth to be ground up by the molars. The front teeth (incisors and canines) play no part in feeding. The amount of food ingested is small relative to the size of the animal but its resting habits by day reduce its energetic demands and food may be retained in the gut longer than most large herbivores. The stomach is a complex four-chambered structure with ruminant-type digestion although Hippos are not true ruminants and do not chew the cud.The ecological requirements for Hippopotamus, therefore, include a supply of permanent or seasonal water, and adequate grazing on open grassland within a few kilometres of the aquatic habitat.

The primary threats to Common Hippos are habitat loss or degradation and illegal and unregulated hunting for meat and ivory (found in the canine teeth).

Habitat loss and conflict with agricultural development and farming are a major problem for hippo conservation in many countries (Brugière et al. 2006, Kanga 2013, Kendall 2013, Brugière and Scholte 2013). Common Hippo’s reliance on fresh water habitats appears to put them at odds with human populations and adds to their vulnerability, given the growing pressure on fresh water resources across Africa (WWC 2004). Habitat loss stems from water diversion related to agricultural development (Cole 1992, Jacobsen and Kleynhaus 1993, Viljoen 1995, Viljoen and Biggs 1998) as well as larger-scale development in and around wetland areas (Jacobsen and Kleynhaus 1993, Harrison et al. 2007). In many West and Central African countries, habitat loss has contributed to a growing regional threat of population fragmentation, as isolated and small populations of hippos are confined to protected areas, with poor or even no management and increasing pressure from local communities (Brugière and Scholte 2013).

 

Reports of human mortalities from Common Hippo interactions have also increased in recent years, another indication of habitat loss. In some agricultural areas, hippo population increases in restricted habitat has also fueled conflict (Kanga 2013). Ten countries reported growing numbers of hippo-human conflicts, in several cases exacerbated by drought conditions. Conflicts with fishermen and gold miners have also been reported (Mackie et al. 2013, Mozambique).  In many countries where Common Hippos are found, populations are not confined to protected areas. Although it is likely that the majority of the overall Common Hippo population reside in some form of protected area (national park, biosphere, game or forest reserve, sanctuary, conservation area), the proportion of protected Hippos likely varies among countries. For countries with a high proportion of Hippo populations outside protected areas, the likelihood of persistence is much lower as there is no impediment to hunting or incentive for habitat protection.

Illegal or unregulated hippo hunting has been found to be particularly high in areas of civil unrest (Kayanja 1989, Shoumatoff 2000, Hillman Smith et al. 2003). At the beginning of 21st century, field surveys found that Common Hippo populations in DR Congo have declined more than 95% as a result of intense hunting pressure, during more than eight years of civil unrest and fighting (Hillman Smith et al. 2003). Similarly, hippo hunting by military forces during civil war in Mozambique during 1980-1992 resulted in decline of more than 70% of the hippo population in the country (Mackie et al. 2013). Widespread poaching for meat has also been reported from Burkina Faso, Burundi, Ivory Coast, and South Sudan (Associated Press 2003, Dibloni 2010, H. Rainey pers. comm.) as well as from politically stable countries like Zambia (Wilbroad and Milanzi 2010). Estimates of the amount of Hippo ivory illegally exported were found to be increasing in the 2008 RLA. A 1994 assessment by TRAFFIC, the monitoring agency of international trade for the IUCN, reported that illegal trade in Hippo ivory increased sharply following the international elephant ivory ban in 1989. Between 1991-1992, approximately 27,000 kg of hippo canine teeth were exported, an increase of 15,000 kg from 1989–1990 estimates (Weiler et al. 1994). In 1997, more than 1,700 Hippo teeth en route from Uganda to Hong Kong were seized by customs officials in France (TRAFFIC 1997). Five thousand kilos of Hippo teeth (from an estimated 2,000 Hippos) of unknown origins were exported from Uganda in 2002 (New Vision 2002). Seizure records of illegal ivory in 2007 and 2008 corroborate that this trend continues as Hippo teeth and products from Hippo teeth have been consistently found with seized ivory and ivory products from elephant tusks.

Although there are several ongoing research projects in captive facilities and with wild populations, little research has focused directly on common hippo conservation. Muwanika et al. (2003) considered the genetic consequences of the intense unregulated hunting that occurred in Uganda in the late 1970s and early 1980s. Based on both nuclear and mitochondrial data, they conclude that although populations were reduced to 70% of initial population size, their current levels of genetic diversity are substantial and not a cause for concern. This suggests that for some populations, once the hunting disturbance is removed, recovery from intense hunting is likely and may not result in detrimental long-term population effects. More recent findings comparing mitochondrial and nuclear DNA suggests that the remaining hippo population currently faces genetic isolation and urges the need for specific protection and regional restoration programmes (Stoffel et al. 2015).

Lewison (2007) evaluates the relative impacts of the known threats to persistence—habitat loss (from agricultural or larger-scale development) and hunting pressure—on a model population. While accounting for rainfall variability and demographic stochasticity, the model results suggest that combinations of habitat loss and even moderate levels of adult mortality from hunting (1% of adults) can lead to relatively high probabilities of population declines over the next 30–40 years.

This species is used as food by humans and for making jewellery, handicraft etc.

This species is listed on CITES Appendix II.
There are numerous protected areas across the countries where Common Hippos are found. Although in most countries the official level of protection is good, the level of enforcement of these regulations is poor in many countries. In some countries, Common Hippos are still found outside of protected areas.