Hippopotamus amphibius


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Hippopotamus amphibius
Species Authority: Linnaeus, 1758
Common Name(s):
English Hippopotamus, Large Hippo, Common Hippopotamus
French Hippopotame
Spanish Hipopótamo Anfibio

Assessment Information [top]

Red List Category & Criteria: Vulnerable A4cd ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Lewison, R. & Oliver, W. (IUCN SSC Hippo Specialist Subgroup)
Reviewer(s): Lewison, R., Oliver, W. ( Pig, Peccary & Hippo Red List Authority) & Hoffmann, M. (Global Mammal Assessment Team)
The 1996 assessment described Common Hippo populations as widespread and secure. Since then, there have been substantial changes in several key countries where Common Hippo are found. The most recent population estimates suggest that over the past 10 years there has been a 7–20% decline in Common Hippo populations. Over three generations (approximately 30 years), it is likely the population reductions will exceed the 30% size reduction considering both past and future. Although the causes of the population decline are known (exploitation and habitat loss), the threats have not ceased, nor is there evidence the threats will be removed in the near future. Therefore, the species is listed as Vulnerable A4cd.
For further information about this species, see 10103_Hippopotamus_amphibius.pdf.
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2006 Vulnerable (IUCN 2006)
2006 Vulnerable

Geographic Range [top]

Range Description:Common Hippos are found in many countries throughout sub-Saharan Africa, and were previously found in virtually all suitable habitats. The species still occupied much of its former range in 1959, although it had disappeared from most of South Africa except for the Kruger National Park (Sidney 1965). They occur in rivers throughout the savanna zone of Africa, and main rivers of forest zone in Central Africa, in Angola, Benin, northern Botswana, Burkina Faso, Burundi, Cameroon, Central African Republic, southern Chad, Côte d’Ivoire, Dem. Rep. Congo, Egypt (extinct; formerly along Nile to its Delta), northern Eritrea, Ethiopia, Equatorial Guinea (Mbini), Gabon, Gambia, Ghana, Guinea, Guinea Bissau, Kenya, Liberia (only two records), Rwanda, Senegal, Sierra Leone, Somalia, Sudan, Swaziland, Malawi, Mozambique, Namibia (Caprivi Strip, Okavango River), Niger, Nigeria, Republic of Congo, Sierra Leone, South Africa (now only in northern and eastern Limpopo Province, eastern Mpumalanga Province, and northern KwaZulu-Natal), Tanzania, Togo, Uganda, Zambia, and Zimbabwe.

The Common Hippopotamus was 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).
Angola (Angola); Benin; Botswana; Burkina Faso; Burundi; Cameroon; Central African Republic; Chad; Congo; Congo, The Democratic Republic of the; Côte d'Ivoire; Equatorial Guinea; Ethiopia; Gabon; Gambia; Ghana; Guinea; Guinea-Bissau; Kenya; Liberia; Malawi; Mali; Mozambique; Namibia; Niger; Nigeria; Rwanda; Senegal; Sierra Leone; Somalia; South Africa; South Sudan; Sudan; Swaziland; Tanzania, United Republic of; Togo; Uganda; Zambia; Zimbabwe
Regionally extinct:
Algeria; Egypt; Mauritania
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: There are clear regional differences in population size and distribution. Eastern African countries (including Uganda, Kenya, Tanzania, Mozambique, and Zambia) form the conservation stronghold for this species and are 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. Populations appear to be decreasing in many countries. The largest populations are found in East Africa. A country-by-country assessment conducted in 1993–1994 found that there were approximately 160,000 Common Hippos across their range, although this was considered to be an overestimate. A more recent assessment suggests that there are likely between 125,000 and 148,000 Common Hippos remaining. In contrast with the 1994 estimate, this range is not likely to underestimate the populations size. Of the 29 countries in which Common Hippos are found, confirmed population declines have been reported in half. The largest declines have occurred in the Democratic Republic of Congo, a country once thought to have the largest populations.

Western Africa
The species is not common in West Africa and the population is split into a number of small groups totalling about 7,000 spread over 19 countries. Populations most at risk are those in West Africa, where the distribution is particularly fragmented.

Hippopotamus are absent from the rain forests except near large rivers. They are most abundant in estuarine habitats and on the lower reaches of rivers. Some are found in the sea in the Archipelago of Bijagos off Guinea Bissau. Guinea, Guinea Bissau and Senegal probably contain the bulk of the West African Common Hippopotamus, with total numbers likely to be in the region of a few thousand. Although small in area, Guinea Bissau supports a substantial population, which is particularly abundant on the islands of the Bijagos Archipelago and along the numerous inland rivers. The species is common on most of the rivers in Guinea and in the east and south of Senegal with an estimated country-wide population of between 500 and 700. The Gambia contains no more than about 40 animals. There are probably less than 200 in Sierra Leone or Mali and none at all in Liberia or Mauritania.

The group of contiguous countries, Côte d’Ivoire, Ghana, Togo, Benin and Burkina Faso, contain a total of, at most, two thousand Common Hippopotamus with the majority in Burkina Faso. There have been no recent counts except on the Comoe River on the border with the Côte d’Ivoire, where 720 were recorded in 1989. A further group is found on the Pendjari River system bordering Benin. This numbered about 500 in 1979 but only some 280 remained in 1987. The Mono River between Benin and Togo supported a small but stable population of 53 in 1986. Only remnant populations remain in Ghana.

Nigeria and Niger between them contain at least 400. No recent information was obtained for Chad but according to Sidney (1965) the species was common in the vicinity of Lake Chad during the 1950s. Common Hippopotamus were also once numerous in Cameroon but the only information obtained during the present survey was from the Korup National Park, where signs of the species are common around the confluence of the Miri and Bake Rivers although sightings are few. It is likely that the species does not occur in the Bake River much further upstream than Bajo although some traces were found as far up as Bakut. At least 150 Common Hippopotamus (possibly as many as 1,500) are known to exist in the Central African Republic in addition to an unknown number in Bamimgui-Bangoran National Park, where 136 were counted in 1973 although now there are probably only 20 to 30 present. Common Hippopotamus occur along most of the coastline of Gabon and for a considerable distance up the Ogooue River and although there are no recent estimates of numbers, they are said to be abundant in places. A few are found in neighbouring Equatorial Guinea on the Campo River. No counts have been made in the Congo, but the species is reported by one correspondent to be widely distributed and numerous on suitable rivers but another reports its presence on only one, the Nyanga River. The entry for the Congo in the IUCN Directory (IUCN/UNEP, 1987) lists Odzala National Park, Lefini Reserve (Louna and Lesio Rivers), and Nyanga North Reserve as containing hippopotamus. Zaire will be considered with East Africa as most of the hippopotamus are in the east of the country.

The total number of Common Hippopotamus in the nineteen west African countries considered here cannot be assessed with any accuracy because of the absence of recent counts but the figure is likely to be in the region of 7,000.

Eastern Africa
East Africa holds substantial numbers with 30,000 in eastern DR Congo and populations numbering tens of thousands in Ethiopia, Sudan and Tanzania. Several thousand also occur in Kenya and Uganda bringing the total for East Africa as a whole to about 70,000.

Many of the Common Hippopotamus in Africa are found in the east, especially in Ethiopia, Kenya, Sudan, Tanzania, Uganda and DR Congo. The Common Hippopotamus occurs in the southern Sudan on the Rivers Nile, Sobat and Jur south of Malakal and in several national parks and reserves. Other localities include the Sudd and tributaries of the Nile. There is no information on population sizes but it is said to occur in good numbers in most places. The species is also abundant between altitudes of 200 and 2,000 m in neighbouring Ethiopia, where its main strongholds appear to be the Omo, Awash and Great Abbi (Blue Nile) Rivers. It also occurs in most of the larger lakes and as isolated populations in smaller swamps and pools. The few that occur in the dry south-east are confined to the Webi, Shebeli and Ganale Rivers. The northern limit of the species is the Setit River. No precise counts have been made recently but the Common Hippopotamus is said to be numerous throughout its range. The total for the two countries combined is probably to be numbered in tens of thousands. Very few animals remain in neighbouring Somalia although some small groups have been reported on the lower Shebeli River and along the Juba River, where they are rather more numerous. No Common Hippopotamus have been reported from Djibouti.

The species occurs in most of the many suitable habitats throughout Kenya and some recent counts have been made in the Mara River area (2,132 in 1980), Lake Naivasha (220 in 1988) and along part of the Tana River between Osako and Adamson's Falls (220 in 1983) (Coe and Collins 1986, Karstad et al. 1980, Smart, in litt). The Mara figure includes some from over the border in Tanzania. Elsewhere in Tanzania, Common Hippopotamus are common in the Selous Game Reserve, where 1,894 were counted on 115 km of the River Rufigi in 1987 (Samuels, in litt). An estimate for the total population of the Selous in 1986 was 16,900 (with a standard error 6,307) from an aerial sample count made by I. Douglas-Hamilton. Independent aerial counts in the Selous reported by Games (1990) returned figure of 15,483 in 1986, 24,169 in 1989 and 20,589 in 1990. The last total is a rather crude extrapolation from an observed figure of 6,866. A large population occurs on the Akagera River and associated lakes on the border between Tanzania and Rwanda, but no recent count has been made. The total counted from the air in 1969 was 671 (Spinage et al. 1972). Common Hippopotamus are found in most other national parks and reserves of Tanzania and although not present anywhere in large numbers, the total probably amounts to several thousand more.

The principal concentrations of the species in Uganda are in the two large national parks, Murchison Falls and Queen Elizabeth. At one time the population in the latter park reached 21,000, but this was reduced to about 14,000 in the 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. Similar numbers were found in the Murchison Falls National Park in the past but there, too, heavy poaching has reduced the population to remnant numbers although a recent count has not been made. The latest appears to have been in 1980 when 1,202 were recorded on the Nile between the falls and Paraa Lodge. The total for the whole park is probably about the same as in Queen Elizabeth National Park i.e., a few thousand. Other regions in Uganda where substantial numbers of hippopotamus occurred include the Semliki River and lakes Victoria and Kyoga. An educated guess of about 7,000 for the present total population of hippopotamus in the whole country is probably not far wrong.

Common Hippopotamus 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 and elsewhere in several national parks including Garamba, Kundelungu, Salonga, Upemba and Virunga. The latter contains the greatest concentration with a total of 22,875 estimated from a 1988 aerial count made by C. Mackie, who with K. Hillman Smith also recorded 2,851 in Garamba National Park in 1988. In round figures, these counts suggest a total of some 26,000 Common Hippopotamus for the two parks. Numbers elsewhere in DR Congo probably do not amount to more than a few thousand, perhaps bringing the country-wide total up to about 30,000.

There are not many Common Hippopotamus in the remaining East African countries of Rwanda and Burundi. Numbers on the Akagera River have been mentioned above in the section on Tanzania and there are probably still a few in wallows within the Akagera National Park or Mutara Game Reserve but no recent information has been received. Common Hippopotamus occur in Burundi on the Malagarazi, Ruvubu and Rusizi Rivers but there are conflicting reports over numbers. P. Chardonnet reports good populations numbered in hundreds and P. C. Trenchard puts the total on these rivers as over 1,000 as a conservative estimate. K. M. Doyle, however, casts doubt on these figures, for along a 120 km stretch of the Ruvubu River where several hundred were reported by P. Chardonnet, he recorded only 39 animals, all but two within the Ruvubu National Park, although there may have been more in wallows etc. away from the river, which were not surveyed.

Although there are many gaps in the data, the above analysis suggests that there could be as many as 70,000 Common Hippopotamus in the east African countries.

Southern Africa
Southern Africa also has flourishing populations, with Zambia containing the biggest population, 40,000, of any country in Africa. Others with large numbers include Mozambique (16,000–20,500), Malawi (10,000), Zimbabwe (6,900) and South Africa (5,000). The total in the whole of the region may be around 80,000.

No information has been received from Angola. According to Sidney (1965), the Common Hippopotamus was widespread throughout Angola particularly in the east on the Cunene, Cubango, Cuando, Cuanza, Longa and Zambezi Rivers.

There are probably more Common Hippopotamus in Zambia than in any other single country. F. E. C. Munyenyembe puts the country-wide total at 40,000 with 20-25,000 in the Luangwa Valley according to R. H. V. Bell. They are reported to be widespread on the Kafue Flats and in Lochinvar National Park. Neighbouring Malawi, although small, is also densely populated with Common Hippopotamus, which occur on all rivers and lakes of sufficient size. The main concentrations are at Elephant Marsh (lower Shire River), the south-west arm of Lake Malawi, Upper Shire River and Lake Malombe in Liwonde National Park. R. H. V. Bell makes a guess that there are some 10,000 Common Hippopotamus in the whole of Malawi. Further south in Zimbabwe, the species is still common. It is found on most of the large rivers particularly the Limpopo. Zambezi and the Sabi/Lundi systems. It is also found in smaller rivers and dams where there is permanent water. Some wander over long distances to provide isolated records. The only estimate for the country-wide total is that made by R. B. Martin on the basis of some limited counts, which have revealed some dense populations e.g. 2,000 on a 50-km section of the Zambezi. His estimate is 6,900, of which 5,530 occur in national parks or reserves, 1,020 on communal lands and 350 elsewhere.

A surprising number of Common Hippopotamus appear to have survived in Mozambique, at least up to 1986, despite the recent civil strife. The species is still widely distributed throughout the country and is present on most river systems. Several national parks and reserves contain hippopotamus although only Gorongosa, with about 2,000, has a sizeable population. L. Tello's estimate made in 1986 year puts the total at between 16,000 and 20,500 for the country as a whole with most (10,000 -12,000) in the Zambezi Wildlife Utilization Area, which includes Marromeu Reserve and four safari hunting blocks. It is also contiguous with the Gorongosa National Park. This is the only region where numbers have increased (by some 20% since 1974). Elsewhere there has been a decline, except in Tete Province, whose population of between 1,500 and 2,500 is said to be stable.

Namibia is too dry to support many Common Hippos except in the north, where the species is present in some numbers on the Cuando and Zambezi Rivers in the Caprivi Strip. Elsewhere it occurs along the boundary with Angola on the Okavango River. Botswana is also too dry, except in the north of the country, where some animals occur in the Okavango Delta and in the Chobe/Linyati River system. A few (18+) exist on the Limpopo in the east. Outside this area, a small population may still exist near Ghanzi although some observers think this is unlikely. C. A. Spinage puts the total in northern Botswana at 1,600 in the wet season and 500 in the dry.

Common Hippopotamus are confined to the north-east of the country in the Republic of South Africa, mainly in the Limpopo, Mpumalanga and North West provinces and the northern tip of KwaZulu-Natal. Most of them are in the Kruger National Park in perennial rivers, dams and the larger pools of seasonal rivers. The total counted in the park in 1989 was 2,761 with 2,575 in rivers and 191 in dams and pools. R. H. Taylor gives a total (for 1986) of 1,264 for KwaZulu-Natal, with the largest concentration (595) on Lake St Lucia, but he suggests a better estimate of 1,423 averaged over the five years 1982-1986. Those in kwaZulu-Natal outside the Kruger National Park are mainly confined to the large rivers in the eastern and northern regions of the province. These figures suggest that there are approaching 5,000 Common Hippopotamus in the country as a whole.

It is not possible to provide a total for the whole of southern Africa because of the lack of data from Angola, which used to support large populations and may do so still, although the disturbed political situation in the country makes it more likely that most hippopotamus have been shot. Assuming the worst and that only a few hundred remain in Angola, a very rough estimate for the regional total would be 80,000.

Follow link below for Table 1: country information including population status, trend, etc.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: 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 it does not eat aquatic vegetation to any extent. Open water is not essential and the animal can survive in muddy wallows but it must have access to permanent water to which it can return in the dry season. The essential factor is that the skin must remain moist for it 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. A curious feature is the red secretion from modified sweat glands, which is thought to have an antibiotic function.

The water body must be large enough to accommodate a number of animals for the Common Hippo is highly gregarious when resting by day. The social habits of the species have been studied by Klingel (1991), who found that the "schools" are unstable groups of females and bachelors. The social system is based on mating territoriality. Common Hippos are gregarious, social, polygymous animals. 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. 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 Hippopotamus, 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 for orientation.

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 probable that the need to avoid the direct rays of the sun has determined the nocturnal feeding habits of the animal. It leaves its wallow soon after sunset and spends the night grazing on short grass swards for up to several kilometres from water. These swards, which are kept short by the activities of the hippopotamus, are known as hippo lawns. Although the hippopotamus grazes every night, except for mothers with very young calves, there are usually animals present in the water all night, as some return after a few hours and others leave later. 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. The stomach is a complex four-chambered structure with a ruminant type digestion although the animal does not chew the cud.

The ecological requirements for hippopotamus, therefore, include a supply of permanent water, large enough for the territorial males to spread out, and adequate grazing on open grassland within a few kilometres of the daytime resting sites.
Systems: Terrestrial; Freshwater; Marine

Threats [top]

Major Threat(s): The primary threats to Common Hippos are illegal and unregulated hunting for meat and ivory (found in the canine teeth) and habitat loss. Illegal or unregulated hunting of Common Hippos has been found to be particularly high in areas of civil unrest (Kayanja 1989; Shoumatoff 2000; Hillman Smith et al. 2003). A recent field survey 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). Widespread poaching for meat has also been reported from Burundi and Ivory Coast (Associated Press 2003; H. Rainey pers. comm.). In many countries were Common Hippos are found, populations are not confined to protected areas; some of these unprotected areas are included in Table 1. Although it is likely that the majority of the total Common Hippo population occurs in some form of protected area (national park, biosphere, game or forest reserve, sanctuary, conservation area), the proportion of protected Common Hippos likely varies among countries. For countries with a high proportion of Common Hippo populations outside protected areas, the likelihood of persistence is much lower as there is no impediment to hunting or incentive for habitat protection.

Estimates of the amount of Common Hippo ivory illegally exported have also increased. 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).

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). Reports of human mortalities from Common Hippo interactions have also increased in recent years. Ten countries reported growing numbers of hippo-human conflicts, in several cases exacerbated by drought conditions.

Although there are several ongoing research projects in captive facilities and with wild populations, little research has focused directly on common hippo conservation. Mwanika 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.

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 a relatively high probabilities of population declines over the next 30–40 years.

Follow link below for Table 1: country information including population status, trend, etc.
For further information about this species, see 10103_Hippopotamus_amphibius.pdf.
A PDF viewer such as Adobe Reader is required.

Conservation Actions [top]

Conservation Actions: 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.

Bibliography [top]

Associated Press. 2003. Hippo population decimated in Burundi, Aloys Niyoyita.

Baillie, J. and Groombridge, B. (comps and eds). 1996. 1996 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

Cole, M. 1992. Zimbabwe’s hippos threatened by drought. New Scientist 134(1817): 9.

Games, I. 1990. A survey of hippopotamus in the Selous Game Reserve, Tanzania. Report to the Director of Wildlife, Tanzania.

Hillman Smith, A. K., Merode, E., Smith, F., Ndey, A., Mushenzi, N. and Mboma, G. 2003. Virunga National Park – North Aerial Census of March 2003. Unpublished report ICCN, ZSL, FZL, IRF, USFWS.

IUCN. 2008. 2008 IUCN Red List of Threatened Species. Available at: http://www.iucnredlist.org. (Accessed: 5 October 2008).

Jacobsen, N. H. G. and Kleynhaus, C. J. 1993. The importance of weirs as refugia for hippopotamus and crocodiles in the Limpopo River, South Africa. Water South Africa 19: 301-306.

Kayanja, F. I. B. 1989. The reproductive biology of the male hippopotamus. Symposium of the Zoological Society of London 61: 181-186.

Lewison, R. L. 2007. Population responses to natural and human-mediated disturbances: Assessing the vulnerability of the common hippopotamus (Hippopotamus amphibius). African Journal of Ecology 45: 407-415.

Manlius, N. 2000. Biogéographie et Ecologie historique de l’hippopotame en Egypte. Belgian Journal of Zoology 130: 59-66.

Mwanika, V. B., Siegismundo, H. R., Bosco, J., Okello, A., Masembe, C., Arctander, P. and Nyakaana, S. 2003. A recent bottleneck in the warthog and elephant populations of Queen Elizabeth National Park, revealed by a comparative study of four mammalian species in Uganda national parks. Animal Conservation 6: 237–245.

New Vision. 2002. UWA Allows Export of Questionable Teeth.

Oliver, W. L. R. 1993. Pigs, Peccaries, and Hippos. IUCN SSC Pigs and Peccaries Specialist Group and Hippos Specialist Group. IUCN – The World Conservation Union, Gland, Switzerland.

PPHSG Hippo Specialist Sub Group. 2004. Specialist Sub Group website. Available at: http://moray.ml.duke.edu/projects/hippos/.

Shambaugh, J., Oglethorpe, J. and Ham, R. 2001. The Trampled Grass: Mitigating the impacts of armed conflict on the environment. Biodiversity Support Program, Washington, DC, USA.

Shoumatoff, A. 2000. Four World Heritage sites in danger in Eastern Congo: Biodiversity conservation in the vortex of civil war. Report to the United Nations Foundation.

TAWIRI. 2001. Total Count of Hippopotamus in Tanzania.

TRAFFIC. 1997. Seizures and prosecutions. TRAFFIC Bulletin 17(1).

Vega, I. 1995. The hippo, threatened due to ivory trade. Quercus, III, Mayo.

Viljoen, P. C. 1995. Changes in number and distribution of hippopotamus (Hippopotamus amphibius) in the Sabie River, Kruger National Park, during the 1992 drought. Koedoe 38: 115-121.

Viljoen, P. C. and Biggs, H. C. 1998. Population trends of hippopotami in the rivers of Kruger National Park, South Africa. In: N. Dunstone and M. L. Gorman (eds), Behavior and Ecology of Riparian Mammals. Symposia of the Zoological Society of London, pp. 251–279. Cambridge Press, London, UK.

Weiler, P., De-Meulenaer, T. and Vanden-Block, A. 1994. Recent trends in the international trade of hippopotamus ivory. TRAFFIC Bulletin 15: 47-49.

World Water Council – WWC. 2004. Analysis of the Third World Water Forum. Secretariat of the 3rd World Water Forum.

Citation: Lewison, R. & Oliver, W. (IUCN SSC Hippo Specialist Subgroup) 2008. Hippopotamus amphibius. In: The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 21 December 2014.
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