Moving beyond the absence of suffering to active measurement and promotion of positive welfare states is the frontier of zoo animal welfare science. Identifying indicators of positive emotions in zoo animals allows evidence-based improvement of quality of life.
The shift from measuring absence of suffering to measuring presence of positive experiences represents a maturation of zoo welfare science. An animal that is not obviously suffering may still have a poor quality of life characterised by boredom, lack of control, and absence of positive experiences. Measuring play, optimistic cognitive bias, and affiliation provides a richer picture of welfare that drives more ambitious environmental improvement. Zoos committed to positive welfare science invest in enrichment programmes, social housing, and choice provision that go beyond minimum standards.