# Pygmy hippopotamus
The **pygmy hippopotamus** (*Choeropsis liberiensis*) is a small, mostly nocturnal, forest-dwelling hippopotamid endemic to the Upper Guinean forest ecosystem of [West Africa](https://www.edgepedia.org/west-africa), and the only extant species in the genus *Choeropsis*. It is one of just two living hippopotamus species, the other being the much larger common hippopotamus (*Hippopotamus amphibius*), and it is classified as Endangered on the IUCN Red List and listed on CITES Appendix II.[1](https://academic.oup.com/mspecies/article/51/982/100/5661028)
| Key fact | Detail |
|---|---|
| Scientific name | *Choeropsis liberiensis* (Morton, 1849); first described as *Hippopotamus minor* in 1844[1](https://academic.oup.com/mspecies/article/51/982/100/5661028) |
| Size | Adults 160–275 kg in captivity, shoulder height 70–80 cm; recorded wild weights 165–204 kg[1](https://academic.oup.com/mspecies/article/51/982/100/5661028) |
| Range | Fragmented populations in Côte d'Ivoire, Guinea, Liberia, and Sierra Leone[1](https://academic.oup.com/mspecies/article/51/982/100/5661028) |
| Conservation status | IUCN Endangered; population estimated at 2,000–2,500 mature individuals and declining[2](https://doi.org/10.2305/IUCN.UK.2015-2.RLTS.T10032A18567171.en) |
| Lifestyle | Solitary or in pairs, more terrestrial than the common hippo, active mainly at night[3](https://www.hipposg.org/pygmy-hippopotamus) |
| Reproduction | Gestation 188–210 days, a single calf of about 5 kg, sexual maturity at 2.5–3 years in managed care[4](https://www.dcceew.gov.au/sites/default/files/env/pages/d8bf16ca-362b-4e6d-9144-4b71770bd6b6/files/pygmy-hippopotamus-department-risk-analysis.pdf) • [3](https://www.hipposg.org/pygmy-hippopotamus) |
| Captive population | Just over 350 animals worldwide in zoological collections[5](https://www.sciencedirect.com/science/article/pii/S004451691500043X) |
## Description and anatomy
The pygmy hippopotamus is the smaller of the two extant hippopotamids. Captive adults weigh 160–275 kg with a shoulder height of 70–80 cm, against a wild common hippopotamus that can weigh upwards of 1,500 kg with a shoulder height of 130–140 cm.[1](https://academic.oup.com/mspecies/article/51/982/100/5661028) The only recorded weights of wild specimens are an adult male at 204 kg and two adult females at 165 and 170 kg.[1](https://academic.oup.com/mspecies/article/51/982/100/5661028) One comparative study measured a pygmy hippopotamus body size of 284 kg against 1,879 kg for the river hippopotamus, more than 6 times smaller, while the brain weighed 306 g against 500 g, only 1.6 times smaller.[6](https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/pygmy-hippopotamus)
Its build reflects a more terrestrial life than that of the common hippo: the body is barrel-shaped with somewhat longer limbs, the head is more torpedo-shaped, and the four toes are only moderately webbed, an adaptation to walking on land.[3](https://www.hipposg.org/pygmy-hippopotamus) The skin is gray, hairless except on the snout and tail, and subdermal glands secrete an oily clear-to-white fluid that protects against sunburn, dehydration, and bacterial infection.[1](https://academic.oup.com/mspecies/article/51/982/100/5661028) Muscular valves close the ears and nostrils under water, and the four-chambered stomach supports microbial fermentation of a high-fiber plant diet.[1](https://academic.oup.com/mspecies/article/51/982/100/5661028) • [4](https://www.dcceew.gov.au/sites/default/files/env/pages/d8bf16ca-362b-4e6d-9144-4b71770bd6b6/files/pygmy-hippopotamus-department-risk-analysis.pdf) The dental formula, i 2/1, c 1/1, p 4/4, m 3/3, totals 38 teeth, one pair of lower incisors fewer than the common hippopotamus's 40.[1](https://academic.oup.com/mspecies/article/51/982/100/5661028)
## Taxonomy and naming
Samuel George Morton first described the species in 1844 as *Hippopotamus minor*, based on differences in cranial morphology and dental formula, but that name was preoccupied by a fossil Cypriot hippo, and Morton replaced it with *liberiensis* in 1849. [Joseph Leidy](https://www.edgepedia.org/joseph-leidy) proposed *Choeropsis*, from the Greek for "pig-like", in 1853.[1](https://academic.oup.com/mspecies/article/51/982/100/5661028) In 1977 Coryndon moved the species into the genus *Hexaprotodon*, and both names circulated in the literature; a 2005 cladistic review by Jean-Renaud Boisserie concluded that the pygmy hippo's mix of primitive and derived features represents a distinct lineage, revalidating *Choeropsis* and restricting *Hexaprotodon* to a fossil lineage found mostly in Asia.[1](https://academic.oup.com/mspecies/article/51/982/100/5661028)
Two subspecies are recognized: the nominate *C. l. liberiensis* of the Upper Guinea forest, and Heslop's pygmy hippo (*C. l. heslopi*) of the [Niger Delta](https://www.edgepedia.org/niger-delta) in Nigeria, described from osteologic specimens collected in 1945. No reliable report of the Nigerian form has been made since 1943, and it is considered possibly extinct.[3](https://www.hipposg.org/pygmy-hippopotamus) Molecular work published in 2023 suggests a Pliocene to Early Pleistocene divergence date between the common and pygmy hippopotamus lineages.[7](https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2023.1144711/full)
## Distribution and habitat
The species is endemic to the Upper Guinean lowland forests of West Africa and survives in fragmented populations in four countries: Côte d'Ivoire, Guinea, Liberia, and [Sierra Leone](https://www.edgepedia.org/sierra-leone).[1](https://academic.oup.com/mspecies/article/51/982/100/5661028) Liberia lies at the center of the range and holds the most extensive tracts of intact lowland forest; in Côte d'Ivoire the most important site is [Taï National Park](https://www.edgepedia.org/tai-national-park) with the adjacent N'Zo Faunal Reserve.[3](https://www.hipposg.org/pygmy-hippopotamus) The historic distribution was far more extensive than today's, and populations have disappeared from many sites and become fragmented.[3](https://www.hipposg.org/pygmy-hippopotamus)
Pygmy hippos inhabit lowland primary and secondary evergreen forests and gallery forests extending into savanna, with a preference for small streams with complex structure such as fallen submerged trees, root-system hollows, swampy areas, and dense vegetation.[3](https://www.hipposg.org/pygmy-hippopotamus) • [4](https://www.dcceew.gov.au/sites/default/files/env/pages/d8bf16ca-362b-4e6d-9144-4b71770bd6b6/files/pygmy-hippopotamus-department-risk-analysis.pdf) Daytime hours are usually spent in or near water, where they use riverbank erosion cavities as hiding places, and they move through the forest on game trails or tunnel-like paths.[3](https://www.hipposg.org/pygmy-hippopotamus)
## Behavior and diet
Pygmy hippos are more solitary than common hippos, occurring alone or in pairs, and are more active at night, though activity is not limited to darkness.[3](https://www.hipposg.org/pygmy-hippopotamus) Home ranges, based on a small number of individuals, are estimated at about 2 km² for males and 0.5 km² for females; limited field studies give female ranges of roughly 40–60 ha and male ranges of about 150 ha, with daily movement of at most 1.5 km.[3](https://www.hipposg.org/pygmy-hippopotamus) • [4](https://www.dcceew.gov.au/sites/default/files/env/pages/d8bf16ca-362b-4e6d-9144-4b71770bd6b6/files/pygmy-hippopotamus-department-risk-analysis.pdf) They mark traveled areas by spreading dung while rapidly wagging the tail.[3](https://www.hipposg.org/pygmy-hippopotamus)
They are believed to browse on leaves, herbs, aquatic plants, fallen fruit, roots, ferns, and tubers, favoring species rich in sodium and protein.[3](https://www.hipposg.org/pygmy-hippopotamus) Feeding appears opportunistic rather than selective: the availability of each plant species seems to determine diet composition. Important foods include gingers (*Aframomum*), [Marantaceae](https://www.edgepedia.org/marantaceae), sedges, and ferns and herbs with high protein and sodium content; fruits and seeds are particularly important.[8](https://strapi.eaza.net/uploads/2020_EAZA_Best_Practice_Guidelines_Pygmy_hippo_approved2_fc7f75526d.pdf) They also feed on crops such as sweet potatoes, okra, pepper, and cassava, though the species is not noted as a crop pest.[4](https://www.dcceew.gov.au/sites/default/files/env/pages/d8bf16ca-362b-4e6d-9144-4b71770bd6b6/files/pygmy-hippopotamus-department-risk-analysis.pdf)
## Reproduction
Almost everything known about reproduction comes from animals under managed care; there is no information on breeding in the wild.[3](https://www.hipposg.org/pygmy-hippopotamus) Captive animals breed throughout the year, with an estrous cycle averaging 35.5 days and estrus lasting 24–48 hours. Gestation lasts approximately 188–210 days, after which a single calf (rarely twins, about one in 200 births) is born on land, weighing about 5 kg.[3](https://www.hipposg.org/pygmy-hippopotamus) • [4](https://www.dcceew.gov.au/sites/default/files/env/pages/d8bf16ca-362b-4e6d-9144-4b71770bd6b6/files/pygmy-hippopotamus-department-risk-analysis.pdf) Calves can swim shortly after birth, and sexual maturity occurs between 2.5 and 3 years of age.[3](https://www.hipposg.org/pygmy-hippopotamus) In captivity individuals have lived up to 56 years.[4](https://www.dcceew.gov.au/sites/default/files/env/pages/d8bf16ca-362b-4e6d-9144-4b71770bd6b6/files/pygmy-hippopotamus-department-risk-analysis.pdf)
## Conservation
The pygmy hippopotamus has been assessed as Endangered, with the population estimated at 2,000–2,500 mature individuals and declining; earlier estimates of 2,000–3,000 may themselves have been too high.[2](https://doi.org/10.2305/IUCN.UK.2015-2.RLTS.T10032A18567171.en) • [3](https://www.hipposg.org/pygmy-hippopotamus) [Deforestation](https://www.edgepedia.org/deforestation) is the biggest threat: forests within the historical range have been logged, farmed, converted to rubber, coffee, and oil palm plantations, and settled. Opportunistic bushmeat hunting poses an additional threat; unlike the common hippo, the pygmy hippo's teeth have little trade value, but body parts such as the skull may be used in rituals or traditional medicine.[2](https://doi.org/10.2305/IUCN.UK.2015-2.RLTS.T10032A18567171.en) The species' range has changed drastically in the past 100 years, most acutely in the last 30, and conflicts in range countries have added further pressure.[3](https://www.hipposg.org/pygmy-hippopotamus)
A Regional Pygmy Hippo Conservation Strategy was developed at a 2010 workshop in Monrovia attended by all range states, and a second workshop there in 2019 updated it.[3](https://www.hipposg.org/pygmy-hippopotamus) Because remaining populations sit mostly inside protected areas, effective management of those areas and maintenance of habitat corridors between fragmented sites are central to the species' persistence.[3](https://www.hipposg.org/pygmy-hippopotamus)
## In captivity and popular culture
The species has been exhibited in zoological collections since the early 1900s but remains uncommon there, with just over 350 animals worldwide; systematic research on the captive population has been limited compared with other large mammals.[5](https://www.sciencedirect.com/science/article/pii/S004451691500043X) An International Studbook and regional breeding programs in Africa, Europe, and North America manage the population.[3](https://www.hipposg.org/pygmy-hippopotamus) Breeding in captivity has been complicated by a shortage of males; only about a dozen calves were born in zoos globally in the year before early 2024.[9](https://apnews.com/article/583b061a728691bd1f618140a1615304) In 2024 the calf [Moo Deng](https://www.edgepedia.org/moo-deng), born at [Khao Kheow Open Zoo](https://www.edgepedia.org/khao-kheow-open-zoo) in Thailand, became a social media sensation, drawing thousands of daily visitors and funding for the zoo's breeding programs for endangered species.[10](https://apnews.com/article/7bd956dd6766d3f1302b3e2c6ac73644)
## References
1. [Flacke, G. L., Decher, J. (2019). Choeropsis liberiensis (Artiodactyla: Hippopotamidae). Mammalian Species 51(982): 100–118.](https://academic.oup.com/mspecies/article/51/982/100/5661028)
2. [Ransom, C., Robinson, P. T., Collen, B. (2015). Choeropsis liberiensis. The IUCN Red List of Threatened Species e.T10032A18567171.](https://doi.org/10.2305/IUCN.UK.2015-2.RLTS.T10032A18567171.en)
3. [Pygmy Hippopotamus, IUCN SSC Hippo Specialist Group.](https://www.hipposg.org/pygmy-hippopotamus)
4. [Department Risk Analysis: Application to add Choeropsis liberiensis to the EPBC Act Live Import List (Australian Government, 2018).](https://www.dcceew.gov.au/sites/default/files/env/pages/d8bf16ca-362b-4e6d-9144-4b71770bd6b6/files/pygmy-hippopotamus-department-risk-analysis.pdf)
5. [The Pygmy Hippopotamus Choeropsis liberiensis: Bringing to Light Research Priorities for the Largely Forgotten, Smaller Hippo Species. Applied Animal Behaviour Science / ScienceDirect.](https://www.sciencedirect.com/science/article/pii/S004451691500043X)
6. [Pygmy Hippopotamus, an overview. ScienceDirect Topics.](https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/pygmy-hippopotamus)
7. [Molecular data suggests a Pliocene–Early Pleistocene divergence date for the common and pygmy hippopotamus. Frontiers in Ecology and Evolution (2023).](https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2023.1144711/full)
8. [EAZA Best Practice Guidelines for the Pygmy Hippopotamus (2020).](https://strapi.eaza.net/uploads/2020_EAZA_Best_Practice_Guidelines_Pygmy_hippo_approved2_fc7f75526d.pdf)
9. [A rare male pygmy hippo born in a Czech zoo debuts his first photoshoot. AP News (2024).](https://apnews.com/article/583b061a728691bd1f618140a1615304)
10. [Thailand's baby pygmy hippo Moo Deng now has an official song in 4 languages. AP News (2024).](https://apnews.com/article/7bd956dd6766d3f1302b3e2c6ac73644)
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*Topic: Encyclopedia › Life and health › Animals › Vertebrates › Mammals › Ungulates*
*Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license