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.

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 (H. 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.

Declining.

Classified as Endangered (EN B1ab(iii)) on the 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.

At present, little is being done to protect wild pygmy hippo populations or their habitat. The species is included on Appendix II of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora). It is fully protected legally in all countries in which it occurs. 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.

There is a successful captive breeding programme underway, with pygmy hippos being held in 131 collections throughout the world, including London Zoo. The species adjusts well to captivity and generally breeds well; the captive population has more than doubled since 1970.

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).

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.

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. 2005. Hexaprotodon liberiensis. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. Downloaded on 17 May 2006.

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.