Pigs, Peccaries and Hippos Status Survey and Action Plan (1993) Chapter 3.2 The Common Hippopotamus, Hippopotamus amphibius. S. Keith Eltringham Status and Action Plan Summary Status category: 2 (widespread and relatively secure); though it is possible that future review of the subspecific taxonomy of this species will result in particular subspecies being accorded more threatened status categories. The common hippopotamus spends the day in water but emerges at night in order to graze on land, often several kilometers from water. It still occurs widely throughout sub-Saharan Africa although its distribution is far from even. Information collected from questionnaires from 34 countries suggests that the total population in the whole of Africa is of the order of 157,000 animals. Few respondents gave actual numbers and the size of populations has largely been estimated by extrapolation from partial counts or based on qualitative observations. 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. East Africa holds substantial numbers with 30,000 in eastern Democratic Republic of 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. 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. Numbers are decreasing in 18 of the countries investigated and are stable in only six. Populations most at risk are those in West Africa, where the distribution is particularly fragmented. The principal threat to survival is the loss of grazing lands to cultivation. There is little evidence as yet that the canine teeth are being used in trade as substitutes for elephant ivory, but if such a trade were to develop, the species would be at serious risk. Consequently, an investigation into the trade in hippopotamus teeth should be given high priority. Other sociological research projects recommended include the extent of the interaction between hippopotamus and agriculture and the possibility of exploiting the hippopotamus on a sustainable yield basis. Recommended biological research projects are mainly concerned with the population sizes of the hippopotamus in countries, which were not covered, or only partially covered, during the present survey. The identification of populations at particular risk or which are of special significance in conservation terms is another priority. Attention should also be paid to countries with large numbers of hippopotamus in order to ascertain population sizes more precisely and to ensure that populations are maintained at their optimal densities. Methods of improving census techniques should be investigated. Introduction The common hippopotamus still occurs widely throughout its range of sub-Saharan Africa, although its distribution is far from even. It is considered to be relatively secure within its range and, from information from a questionnaire survey, a conservative estimate of the whole population in Africa is in the order of 157,000 animals. Although the survey results confirmed the wide distribution of the species they also indicated that numbers have decreased in many areas. There are said to be five subspecies but little recent research has been carried out and it is possible that this is no more than a classification of museum specimens (also see Grubb, 1993 [also this website]). Lydekker (1915) recognizes the following subspecies: H. a. amphibius - East Africa and west to the Gambia. H. a. tschadensis - Chad and Nigeria. H. a. kiboko - Kenya and Somalia. H. a. constrictis - Angola and Namibia. H. a. capensis - Zambia and south to South Africa. Even if valid, these subspecies cannot be distinguished in the field and none of the correspondents used subspecific names. The alleged ranges are also indistinct. Consequently, the hippo populations in this account are treated on a geographical rather than a taxonomic basis. However, it is quite possible that future reviews of the species' taxonomy will reveal regional genetic characteristics that merit subspecific attribution and that one or more subspecies/geographically distinct populations should be accorded a more threatened status category (see later text). Former and Present Distribution In order to obtain information about the current status of the common hippopotamus, correspondents in countries where the species was known or thought to occur were approached in 1989 and asked to complete a questionnaire, which was the same as that used by the Pigs and Peccaries Specialist Group. If information was not available from residents, it was obtained from persons with recent experience of the countries concerned. Replies were received from 55 correspondents covering 34 countries. The only country believed to contain sizeable numbers of hippopotamus but which was not included in the survey was Angola. The distributions and estimated numbers are based on the replies received and there may well be groups, which have not been recorded. The totals given, therefore, are conservative. The common hippopotamus was previously found throughout Africa south of the Sahara in all suitable habitats. The species still occupied much of its former range in 1959 (Fig. 5), although it had disappeared from most of South Africa except for the Kruger National Park (Sidney, 1965). The results of the recent survey of the species for this account revealed that although the hippopotamus remains widely distributed, its numbers appear to have decreased in many areas. It is still abundant in East Africa where the majority of the population occurs. Because of the uneven distribution, this account will deal with each region in turn, beginning with the distribution and, where possible, the numerical status of the species. Link to Fig. 5: Approximate current and former (c. 1959) distribution of the common hippopotamus (Hippopotamus amphibius). Western Africa 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. Few correspondents were prepared to assess the population size of hippopotamus and it is difficult to interpret their estimates in terms of varying levels of abundance, but it seems that the species is at least locally abundant in several of the countries. Those in the west - Guinea, Guinea Bissau and Senegal - probably contain the bulk of the west African 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, Ivory Coast, Ghana, Togo, Benin and Burkina Faso, contain a total of, at most, two thousand hippopotamus with the majority in Burkina Faso. There have been no recent counts except on the Comoe River on the border with the Ivory Coast, 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. 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 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. 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 neighboring 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 Niangua 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. Democratic Republic of Congo will be considered with East Africa as most of the hippopotamus are in the east of the country. The total number of 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 Many of the hippopotamus in Africa are found in the east, especially in Ethiopia, Kenya, Sudan, Tanzania, Uganda and Democratic Republic of Congo. The 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 neighboring 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 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 hippopotamus remain in neighboring Somalia although some small groups have been reported on the lower Scebeli River and along the Juba River, where they are rather more numerous. No 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 & Collins, 1986; Karstad et al, 1980; Smart, in litt.). The Mara figure includes some from over the border in Tanzania. Elsewhere in Tanzania 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). 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 program 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. Hippopotamus have a wide distribution in the Democratic Republic of 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 hippopotamus for the two parks. Numbers elsewhere in the Democratic Republic of 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 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. 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 hippopotamus, 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 hippopotamus in the east African countries. Southern Africa No information has been received from Angola. According to Sidney (1965), the hippopotamus was widespread throughout Angola particularly in the east on the Cunene, Cubango, Cuando, Cuanza, Longa and Zambezi Rivers. There are probably more 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 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 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 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 hippopotamus 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 for hippopotamus except in the north of the country, where some 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. Hippopotamus are confined to the north-east of the country in the Republic of South Africa, mainly in the Transvaal and the northern tip of 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 Natal and Kwazulu, 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 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 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. Summary A tentative total has been given for the number of hippopotamus in each of the three regions of Africa. These estimates included a high proportion of guesswork in each case and consequently, any figure for the total number of the species in the continent must be regarded with skepticism. Nevertheless, even a rough estimate is of interest and if the sectional totals are summed, the result is 157,000 hippopotamus in the whole of Africa. Although this is unlikely to be an accurate figure, it does suggest that the species is still abundant in many parts of Africa and the next step is to assess its conservation status in terms of population trends and legal status. This follows in Table 4, in which the situation in each country is briefly summarized.
TABLE 4. Population trends, legal status and occurrence of the common hippopotamus, Hippopotamus amphibius, in protected areas, based on returns from the 1989/90 African Suiform Questionnaire Survey.
Country	Popn Status	Popn Trend	Concern?	Legal Protection	Enforcement?	Protected Areas
Angola	No recent information
Benin	RD-LA	D	N	U	P	Pendjari N.P.; "W" N.P. Pendjari H.Z.; Djona H.R; Wari Maro F.R; Mt. Koufee F.R
Botswana	RD-LD	D	N	G	F	Chobe N.P.; Makgadikgadi Pan G.R.; Moremi G.R.
Burkina Faso	RD-LD	D	Y	H	P	"W" N.P.; Arly F.R.; Deux Bales F.R.
Burundi	RD-LA	U	N	G	G	Ruvubu N.P.; Rusizi N.R.; Rwihinda N.R. Kigwena Forest N.R.; Lake
Cameroon	W -LD	U	Y	G	F	Benoue N.P.; Bouba Ndjida N.P; Faro NP; Kalamaloue N.P.; Korup N.P.; Pangar-Djerem H.R.
Central African Republic	RD-LA	D	Y	G	P	Andre Felix N.P.; Bamingui-Bangoran N.P; Manovo-Gounda-Saint Floris N.P; GribinguimF.R.; Koukourou F.R.; Yata- Ngaya F.R;
Chad	No recent information
Congo	W-LA	I	N	G	U	Odzala N.P.; Nyanga Nord F.R. Lefini F.R; Tsoulou F.R.
Equatorial Guinea	RD-LD	U	N	G	P	None
Ethiopia	W-LA	S	N	G	F	No information
Gabon	W-LD	D?	N	G	P	Wonga-Wongue N.P; Lope F.R.; Moukalaba F.R.; Sette-Cama F.R.
The Gambia	RD-LD	D?	Y	G	F	Gambia River N.P
Ghana	RD-LD	D?	Y	G	G	Bui N.P.; Digya N.P.; Mole N.P.
Guinea	W-LA	D	Y	G	G	Badiar N.P.; Ziama B.R.
Guinea Bissau	RD-LA	D?	Y	G	U	None
Ivory Coast	RD-LD	D	Y	H	P	No information
Kenya	W-LA	S	N	G	G	Amboseli N.P.; Lake Nakuru N.P. Meru N.P.; Nairobi N.P.; Tsavo N.P.; Buffalo Springs N.R.; Kora N.R.; Lake Bogoria N.R; Masai Mara N.R. Mwea N.R; North Kitui N.R; Samburu N.R.
Liberia	Probably extinct
Malawi	W-LD	S	N	H	G	Kasungu N.P.; Lake Malawi N.P.; Liwonde N.P.; Vwaza Marsh G.R.; Nkhotakota G.R.; Mwabvi G.R.
Mali	RD-LD	U	Y	U	U	Boucle du Baoule N.P.
Mauritania	Probably extinct
Mozambique	W-LA	D	Y	H	U	Gorongosa N.P.; Gile G.R.; Maputo G.R.; Marromeu G.R.; Niassa G.R.
Namibia	RD-LA	U	Y	G	G	Mudumo N.P. (?); Nkasa N.P.; Western Caprivi G.R.
Niger	RD-LA	D	Y	G	F	"W" N.P.
Nigeria	RD-LD	D	Y	H	F	Kainji Lake N.P.; Kwiambana G.R.; Sambisa G.R.; Yankari G.R.
Rwanda	No recent information
Senegal	RD-LA	D	Y	G	P	Niokolo-Koba N.P
Sierra Leone	RD-LD	D	Y	G	P	Outamba-Kilimi N.P.; Tiwai G.S
Somalia	RD-LD	D	Y	U	P	None
South Africa	RD-LA