Hippopotami are highly aquatic animals with specific needs for deep water, space and social structure. Their welfare in zoo collections raises fundamental questions about appropriate keeping standards.
Hippo welfare in zoos is constrained by the animals' substantial physical requirements - deep pools, large land areas, complex social management - that only the best-resourced facilities can meet. Hippos that cannot fully submerge in their pool are deprived of a core thermoregulatory behaviour. Hippos kept in inappropriate social groupings experience chronic aggression and injury. The welfare case for keeping hippos in zoos rests on their conservation status (vulnerable in the wild) and the educational value of displaying Africa's most dangerous large animal. But the welfare cost to individuals in inadequate facilities is high, and standards should require full submersion capability and appropriate social group provision as minimum requirements.