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The pygmy hippopotamus (''Choeropsis liberiensis'' or ''Hexaprotodon liberiensis'') is a small hippopotamid native to the forests and swamps of West Africa, primarily in Liberia and small populations in Sierra Leone, Guinea and Ivory Coast. The pygmy hippo is reclusive and nocturnal. It is one of only two extant species in the Hippopotamidae family, the other being its much larger cousin the common hippopotamus (''Hippopotamus amphibius''). The pygmy hippopotamus displays many terrestrial adaptations, but like its larger cousin, it is semi-aquatic and relies on proximity to water to keep its skin moisturized and its body temperature cool. Behaviors such as mating and giving birth may occur in water or on land. The pygmy hippo is herbivorous, feeding on ferns, broad-leaved plants, grasses and fruits it finds in the forests. A rare nocturnal forest creature, the pygmy hippopotamus is a difficult animal to study in the wild. Pygmy hippos were unknown outside West Africa until the 19th century. Introduced to zoos in the early 20th century, they breed well in captivity and the vast majority of research is derived from zoo specimens. The survival of the species in captivity is more assured than in the wild; the World Conservation Union estimates that there are fewer than 3,000 pygmy hippos remaining in the wild.〔 Pygmy hippos are primarily threatened by loss of habitat, as forests are logged and converted to farm land, and are also vulnerable to poaching, hunting for bushmeat, natural predators and war. Pygmy hippos are among the species illegally hunted for food in Liberia. == Taxonomy and origins == Nomenclature of the pygmy hippopotamus reflects that of the hippopotamus. The plural form is pygmy hippopotami (''hippopotamuses'' is also accepted as a plural form by the OED, or ''pygmy hippos'' for short). A male pygmy hippopotamus is known as a ''bull'', a female as a ''cow'', and a baby as a ''calf''. A group of hippopotami is known as a ''herd'' or a ''bloat''.〔List of animal names〕 The pygmy hippopotamus is a member of the family Hippopotamidae where it is classified as a member of either the genus ''Choeropsis'' ("resembling a hog") or, the genus ''Hexaprotodon'' ("six front teeth"). Members of Hippopotamidae are sometimes known as hippopotamids. Sometimes the sub-family Hippopotaminae is used. Further, some taxonomists group hippopotami and anthracotheres in the superfamily ''Anthracotheroidea'' or ''Hippopotamoidea''. A sister species of the pygmy hippopotamus may have been the little-studied Malagasy pygmy hippopotamus (''Hexaprotodon madagascariensis'' or ''Hippopotamus madagascariensis''), one of three recently extinct species from Madagascar. ''C. madagascariensis'' was the same size as ''C. liberiensis'' and shared its terrestrial behavior, inhabiting the forested highlands of Madagascar, rather than open rivers. It is believed to have gone extinct within the last 500 years. The taxonomy of the genus of the pygmy hippopotamus has changed as understanding of the animal has developed.〔〔〔〔 Samuel G. Morton initially classified the animal as ''Hippopotamus minor'', but later determined it was distinct enough to warrant its own genus, and labeled it ''Choeropsis''. In 1977, Coryndon proposed that the pygmy hippopotamus was closely related to ''Hexaprotodon'', a genus that consisted of prehistoric hippos mostly native to Asia.〔 This assertion was widely accepted,〔〔〔〔 until Boisserie asserted in 2005 that the pygmy hippopotamus was not a member of ''Hexaprotodon'', after a thorough examination of the phylogeny of Hippopotamidae. He suggested instead that the pygmy hippopotamus was a distinct genus, and returned the animal to ''Choeropsis''.〔〔〔 All agree that the modern pygmy hippopotamus, be it ''H. liberiensis'' or ''C. liberiensis'', is the only extant member of its genus. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pygmy hippopotamus」の詳細全文を読む スポンサード リンク
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