Hippopotamuses are large, semi-aquatic mammals with specific welfare needs related to water access, social structure, and territorial behaviour.
Hippopotamus welfare in zoos is fundamentally defined by water access and quality. These are obligate semi-aquatic animals whose physiology requires continuous water access — not as enrichment or preference but as a physiological necessity. Their skin is not waterproof and desiccates rapidly without immersion; the distinctive pink secretion sometimes called "blood sweat" is a sunscreen and antimicrobial compound that supplements water protection. Inadequate pool volume, poor water quality, or restricted water access time directly harms these animals at a physiological level. Social management of common hippos requires experienced staff — territorial disputes can result in serious injuries and deaths in inadequate facilities. The growing advocacy for retiring common hippos from inadequate zoo facilities to larger sanctuaries reflects the difficulty of meeting their needs in traditional zoo enclosures.