Chimpanzees, gorillas, bonobos, and orangutans have the most complex cognitive and social needs of any zoo-kept animals, making their welfare one of the most challenging areas in zoo management.
Great apes are cognitively the most similar to humans of any zoo-kept species. Their social intelligence, emotional complexity, and capacity for suffering are well-documented. Apes in poor welfare conditions show depression, stereotypic behaviour, and self-harm. Even in excellent facilities, the cognitive deprivation of captivity relative to wild life is significant. The strongest welfare case is for genuinely large, cognitively complex environments with stable social groups. Sanctuaries for apes rescued from research or entertainment provide relevant models.