Modern zoo welfare assessment is shifting from measuring the absence of suffering to measuring the presence of positive welfare states — a fundamental conceptual advance.
The shift toward positive welfare assessment in zoos represents a genuine conceptual advance in animal welfare science. An animal can be free from suffering but not flourishing — not experiencing the positive states that characterise a good life for that species. Recognising play, curiosity, social bonding, and voluntary exploration as welfare indicators alongside stress and stereotypy gives a fuller picture of zoo animal welfare. This approach is more demanding: it requires knowing what positive states look like for each species, observational training to detect them, and willingness to act when they are absent. The best zoos are adopting this framework and finding it reveals welfare opportunities invisible to deficit-only assessment.