Pygmy hippopotamus  (Choeropsis liberiensis)

Classified as Endangered (EN) by the IUCN Red List (1), and listed on Appendix II of CITES (3).

The pygmy hippopotamus shares the barrel-shaped body form of the closely related common hippopotamus (Hippopotamus amphibius), but is considerably smaller. Other physical differences between the two hippopotamus species include the placing of the eyes, which are more towards the side of the head in the pygmy hippopotamus, feet that are not as webbed as in the common hippopotamus (2), and the pygmy's sloping smooth, greenish-black back (7). The sexes are similar in appearance; as males do not have a scrotum, males and females are very difficult to tell apart (7). The name hippopotamus derives from the Greek for 'river horse' (2). Genetic studies have revealed that hippopotami share a common ancestor with whales (2), while recent fossil evidence alludes to a close relationship between whales and all ungulates (7).

The pygmy hippopotamus is found in western Africa, mainly in Liberia but also in Sierra Leone, Guinea, and the Ivory Coast (2) (4).

Inhabits rivers and swamps in a handful of dense lowland forest patches (6).

The pygmy hippopotamus spends the day in water, and emerges at night to feed on fruits, leaves, roots and grasses (2), which it bites with the thick lips rather than with the teeth (2). Hippopotami have extraordinarily high rates of water loss (three to five times the rate in man) due to their unique skin structure; this explains why they must spend the day in water (2). Pygmy hippopotami usually live alone unless they are mating or with a calf, and they are not thought to hold territories (2). The home ranges of various individuals often overlap, but individuals seem to actively avoid encounters with others, possibly through dung marking (5). In the breeding season, males seek out females and form consortships for a time prior to mating, which tends to occur in the water but may also occur on land (2). Gestation lasts about 6.5 months, calves are suckled for six to eight months and stay with their mother until around eight years of age, when they are fully grown (2). The pygmy hippopotamus is not a particularly vocal species, but has been recorded grunting, hissing, squeaking and snorting (5).

Deforestation is the main threat facing the pygmy hippopotamus (2). Hunting is also known to occur, but the extent of this has not been determined (2). The subspecies C. l. heslopi in Nigeria may already be extinct (2).

Direct conservation action is required to prevent precipitous declines and potential extinction (7). At present there is a good captive population, which has bred successfully in captivity and has doubled in size over the last 25 years (2). If the wild population becomes extinct, it should be possible to maintain the species in captivity, providing a last-ditch safeguard against total extinction (2).

To learn more about a Whitley Award-winning conservation project for this species, click here.

View information on this species at the UNEP World Conservation Monitoring Centre.

For further information on hippopotami see: 

• The IUCN Hippo Specialist Sub Group:
  http://moray.ml.duke.edu/projects/hippos/

To learn about efforts to conserve the pygmy hippopotamus see:

• EDGE of Existence:
  http://www.edgeofexistence.org/mammals/species_info.php?id=21