Hippopotamuses have very specific welfare needs related to water access, social grouping, and space that make truly good captive welfare challenging to achieve.
Hippos that lack sufficient water access develop skin problems including cracking and sunburn — their pink secretion that looks like sweat is actually a natural sunscreen and antimicrobial moisturizer that does not function as a substitute for water immersion. Social groups in zoos are often too small and space too limited for natural behavior. Hippos in the wild establish complex territorial systems along rivers that cannot be replicated in zoo settings. Welfare improvement requires large water features, appropriate social groups, and recognition of hippo behavioral complexity.