Pygmy Hippopotamus
(Choeropsis liberiensis)
The name hippopotamus derives from the Greek for 'river horse', and is a particularly apt description for the pygmy hippo, which spends much of its time resting in rivers or swamps. The species has a severely fragmented distribution and is under increasing pressure from logging, farming and human settlement. The small isolated Nigerian population is thought to be extinct. There have been no confirmed reports of this distinct subspecies for decades, although unofficial reports from local people provide some encouragement that they may still exist.
Urgent Conservation Actions
Surveys to ascertain the status and distribution of the species throughout its range, and focused conservation attention on populations in secure regions.
West Africa (Liberia, Sierra Leone, Guinea, Nigeria and the Ivory Coast).
Pygmy hippos feature in many folktales. One suggests that the pygmy hippo finds its way through the forest at night by carrying a diamond in its mouth, which lights its path. The hippo is said to hide the diamond by day where it cannot be found. According to folklore, if a hunter is lucky enough to catch one at night, the diamond can be taken.
Associated Blog Posts
19th Dec 11
Camera traps are revolutionising our ability to track the changing fate of wildlife. Often used in remote locations looking for elusive species, thi...  Read

15th Oct 11
Trying to get cameras in the wild to capture images of the elusive pygmy hippo (Choeropsis liberiensis) is no easy task, but the project in Sapo National Par...  Read

28th Sep 11
The pygmy hippo is a priority EDGE mammal endemic to the threatened Upper Guinea Forests biodiversity hotspot with fewer than 3,000 believed to remain in the...  Read

7th Jun 11
Today Sapo, the cute pygmy hippo calf at Whipsnade Zoo, took his first dip in the outdoor pool! The calf has been named after the national park in Liberi...  Read

8th Feb 11
In November 2010 a workshop was held in Liberia, West Africa to develop a conservation strategy for the pygmy hippo, EDGE mammal number 29. The pygmy hippo i...  Read

25th Feb 10
The pygmy hippopotamus is today featured as the IUCN Red List ‘Species of the Day’, which is running throughout 2010 to mark the International Year of Bi...  Read

29th Jun 09
EDGE Fellow John Konie recently wrote to give us the news that the President of Liberia had made a visit to Sapo National Park, where Konie is using camera t...  Read

11th Dec 08
Marwell Zoological Park is celebrating the birth of a pygmy hippopotamus, EDGE Mammal species number 21. Born three weeks ago, the hippo is part of a cons...  Read

3rd Jul 08
Our EDGE Fellow John Konie monitors the pygmy hippopotamus and other threatened mammal species in Liberia. He has sent us the following information about Sap...  Read

11th Apr 08
Sapo National park comprises 1800 km2 of moist tropical lowland rainforest, with a varied mosaic of riparian, seasonally inundated, and dryland forest. Ther...  Read

10th Mar 08
Team 1 - forest team While the cameras must stay in the field for 35 days to allow sufficient time for images to be captured, in order to complete the train...  Read

4th Mar 08
On the 20th January, Ben Collen, Janna Rist and Olivia Daniel set off to Liberia to set up a monitoring programme in Sapo National Park, and to try and captu...  Read

20th Jan 08
Today we travel out to Sapo National Park to begin our pygmy hippo monitoring programme.  All the camera traps arrived last week thanks to Rich (at www.trai...  Read

12th Oct 07
Robert Howard, part of the Fauna and Flora International (FFI) team carrying out the biomonitoring programme in Sapo National Park sent us this blog:  ...  Read

23rd Aug 07
Hi I’m John Konie, I currently work as a Biologist for the Forestry Development Authority (FDA), in Liberia. Recently I have been given a great opportunity...  Read

Evolutionary Distinctiveness
Order: Artiodactyla
Family: Hippopotamidae
Hippopotami were formerly believed to be most closely related to pigs or peccaries. However, recent genetic studies have revealed that their closest living relatives are in fact whales. The ancestors of both whales and hippos were small water-loving terrestrial mammals that lived 50-60 million years ago. These groups diverged during the Eocene (around 54 million years ago) into the early cetaceans, which became completely aquatic, and a large and diverse group of pig-like terrestrial mammals known as anthracotheres. The anthracotheres flourished for 40 million years, evolving into at least 37 distinct genera, and dispersing to all continents except for the then-isolated landmasses of Australasia and South America. The earliest known hippopotami are believed to have evolved in Africa around 16 million years ago. Around 2.5 million years ago, most of these species became extinct, with just five species surviving into historical times. Three of these species are known only from Madagascar, and have probably been extinct for over 100 years. Only two species of hippopotamus survive today in two genera: Hippopotamus amphibius (common hippopotamus) and Choeropsis liberiensis (pygmy hippopotamus).
Head and body length: 1,500-1,750 mm
Shoulder height: 750-1,000 mm
Tail length: 200 mm
Weight: 160-270 kg
The pygmy hippopotamus looks superficially like a smaller version of the closely related common hippopotamus. Both species are characterised by a broad snout, a large mouth, a short, barrel-shaped body and short stocky legs. There are, however, noticeable physical differences between the two species. The pygmy hippo’s head is more rounded and the eyes are set on the side of the head rather than the front. Its smooth, almost hairless skin is greenish black above, fading to grey on the sides and greyish-white below. It has well separated toes with sharp nails, unlike the common hippopotamus which has webbed feet. The pygmy hippo’s incisors and canines are tusk-like and grow rapidly. The ears and large, rounded nostrils can be closed when the animal is under water. The skin of both species contains special pores that secrete a white or pinkish substance known as “blood-sweat”. This material is thick, oily and protective in nature, allowing the animals to remain in water or in a dry atmosphere on land for extended periods.
The species is less social than the common hippopotamus and is primarily nocturnal. Individuals spend most of the day resting in swamps, wallows or rivers, or in hollows along the sides of streams. They emerge to feed on vegetation during the late afternoon and at night, travelling on a network of paths that tunnel through the thick vegetation. The diet is exclusively vegetarian, consisting of plants, grasses, tender shoots, leaves and fallen fruit. Pygmy hippos are not thought to be territorial. In one study females were found to have overlapping home ranges of around 40-60 ha, whereas a male occupied an area of 165 ha that contained several female ranges. Despite such overlap the species is normally solitary. Individuals are thought to actively avoid one another through dung marking (a practice which involves wagging the tail vigorously from side to side during defecation, scattering the faeces over nearby plants). Males and females meet only briefly in order to mate. There is no accurate data on reproduction in the wild for this species. Pygmy hippos are known to breed throughout the year in captivity. Sexual maturity is attained at 4-5 years of age. Normally a single young is born in a well developed state following a gestation period of 184-204 days. Weaning occurs at 6-8 months. The lifespan of the species in the wild is not known, although one captive individual was reported to live for more than 43 years. The effects of predators on pygmy hippo populations are unknown, although it is thought that leopards may be capable of preying on the species.
Associated with streams in wet forests and swamps.
The species has a discontinuous distribution in western Africa. The largest populations of H. l. liberiensis are in Liberia. Smaller populations occur in Sierra Leone, Guinea, and the Ivory Coast, primarily in regions bordering Liberia. There have been reports of an isolated population in Guinea Bissau based on a report of a hunter having killed a pygmy hippo. However, this individual is more likely to have been a small common hippo.

The second subspecies, H. l. heslopi, is known only from the Niger Delta east to the vicinity of the Cross River in Nigeria. This isolated population is some 1,800 km to the east of known populations of H. l. liberiensis.

The pygmy hippo’s range does not overlap with that of the common hippopotamus.
Population Estimate
In 1993 the IUCN/SSC Hippo Specialist Subgroup estimated that the total remaining population was approximately 2,000–3,000 individuals. The 1993 population estimate for Sierra Leone, the only country with an estimated population size, was 80-100 individuals. Subsequent reports of habitat loss and hunting suggest that the population has declined further since the 1993 estimates.

The Nigerian subspecies (C. l. heslopi) is believed to be extinct. There have been no confirmed reported of this subspecies for decades, although unofficial reports from local people provide some encouragement that they may still exist.
Population Trend
Classified as Endangered (EN C1) on the 2010 IUCN Red List of Threatened Species. The Nigerian subspecies is classified as Critically Endangered (CR D).
The range of the pygmy hippopotamus is severely fragmented, and is continuing to decline in area, extent and quality as a result of logging, farming and human settlement. In Liberia, where the largest populations of pygmy hippos occur, deforestation is occurring at an alarming rate, with more than 190 million cubic metres of wood having been exported from the country since 1999. The species is under increasing pressure from bushmeat hunters as the forests become smaller and more accessible. Although pygmy hippos are unlikely to be the main target of subsistence hunting, they are taken opportunistically by the hunters, and this is likely to be impacting upon the remaining small, isolated populations. National and international conflicts in eastern Sierra Leone, Guinea and Liberia are also likely to be having a negative effect on the species. The border area between Guinea and Liberia in particular has been under increasing pressure from the impacts of Liberian war refugee settlements. According to the IUCN/SSC Hippo Specialist Subgroup, unless effective protection or conservation actions are taken, the viability of this species should be considered extremely low.
Conservation Underway
Pygmy hippos are included on Appendix II of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora). They are fully protected legally in all countries in which they occur. However, enforcement is limited due to a lack of resources and civil unrest. The 509 square-mile Sapo National Park in eastern Liberia supports an important population of pygmy hippos. Protection here has been relatively good in the past, although there are recent reports of hunting occurring within the park’s boundaries. Another key area in which the species occurs is in the Tai National Park in western Côte d'Ivoire. However, this area is now subject to poaching, agricultural encroachment and gold mining in the park's river beds.

In 2007 the EDGE team highlighted the pygmy hippo as an EDGE Focal Species due to the limited conservation attention it was receiving. Since then we have supported an EDGE Fellow to carry out monitoring of pygmy hippos in Sapo National Park Liberia, as part of a wider biomonitoring programme established by Fauna and Flora International (FFI) and Liberia’s Forest Development Authority (FDA). Sapo National Park is home to one of the largest remaining populations of pygmy hippos, and the information collected will help to inform the development of the park management plan, and ensure that conservation actions are appropriate.

In Sierra Leone, conservation biologists from the Zoological Society of London (ZSL) are working with researchers at Njala University to determine the current distribution of the species and estimate population numbers. Also in Sierra Leone, the Gola Forest Programme, a collaboration between the Royal Society for the Protection of Birds (RSPB), the Conservation Society of Sierra Leone and the National Commission on the Environment and Forestry, are working in the Gola Forest Reserve, one of the few remaining sites in Sierra Leone known to harbour a significant population of pygmy hippos.

Whilst in the Ivory Coast the Royal Zoological Society of Scotland (RZSS), the Institute for Breeding of Endangered African Mammals (IBREAM) and the Swiss Centre of Scientific Research (CSRS) are monitoring the pygmy hippo population in Tai National Park with a view to developing a management plan.

In 2009 the IUCN SSC Hippo Specialist Group endorsed the creation of a pygmy hippo subgroup. This subgroup is in the process of developing a pygmy hippo conservation strategy, to identify threats and priority sites and areas for conservation and research activities needed to ensure the survival of the pygmy hippo in the wild.

There is a successful captive breeding programme underway, with pygmy hippos being held in 134 collections throughout the world, including ZSL London Zoo. The species adjusts well to captivity and generally breeds well; the captive population has more than doubled since 1970.

A camera trap survey has been initiated to monitor pygmy hippos in Sapo National Park, Liberia.

This project supports in-country EDGE Fellows to help conserve relevant EDGE species

To ensure the survival of the pygmy hippopotamus throughout its range.

To ensure the survival of the pygmy hippopotamus throughout its range.

Conservation Proposed
Immediate action is required to ensure the survival of the species. The IUCN SSC Hippo Specialist Subgroup recommends that the distribution and numbers of the species are established throughout its range, particularly in Liberia, where the majority of individuals occur. Effective habitat protection is critical, through the extension of the protected areas network and adequate enforcement of legislation against hunting and logging in these areas. There is an urgent need for the development of sustainable forest management practices, improved control of human settlements and subsistence farming activities in and around protected areas, and comprehensive public education and awareness programmes. An attempt should be made to establish whether or not the isolated population reported from Nigeria still exists. If this population is found to have survived then a recovery plan must be developed to ensure its future protection. Captive breeding efforts should continue, but efforts should focus on improving the conditions under which captive individuals are kept (many deaths in captivity are thought to be due to stress from artificial conditions, which are often vastly different to conditions in the wild). There is currently a skewed sex ratio and a high infant mortality in the captive population, so research into the cause of this is of high priority.
Associated EDGE Community members

Ben heads the Indicators and Assessment Unit at the Institute of Zoology, Zoological Society of London

Ben is involved in a pygmy hippo project in Liberia

Konie is working in Sapo National Park, Liberia, to establish conservation monitoring and actions for the Pygmy hippo ( Hexaprotodon liberiensis)

Conservation geneticist: Wildgenes laboratory

West and North Africa Programme Manager

IUCN Hippo Specialist Subgroup
Pigs, Peccaries and Hippos Specialist Group (PPHSG) of the Species Survival Commission (SSC ). Promotes scientifically-based action for the conservation of common and pygmy hippos.

Zoo population

There are pygmy hippopotamuses resident at both ZSL London and ZSL Whipsnade Zoos.


Boisserie, J-R., Lihoreau, F. and Brunet, M. 2005. The position of Hippopotamidae within Cetartiodactyla. Proceedings of the National Academy of Sciences of the United States of America 102(5): 1537-1541.

Eltringham, S.K. 1993. The Pygmy Hippopotamus (Hexaprotodon liberiensis). In: Oliver, W. L.R. (ed.). Pigs, Peccaries and Hippos. Status Survey and Conservation Action Plan. Pp: 55–60. IUCN, Gland, Switzerland.

IUCN Hippo Specialist Subgroup

Lewison, R. & Oliver, W. 2008. Choeropsis liberiensis. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. www.iucnredlist.org. Downloaded on 12 November 2010.

Nowak, R.M. 1999. Walker's Mammals of the World. Sixth edition. The Johns Hopkins University Press, Baltimore and London.

Distribution map based on data provided by the IUCN Global Mammal Assessment.

if you can provide new information to update this species account or to correct any errors, please email us at info@edgeofexistence.org

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