Environmental enrichment for zoo animals has evolved from basic provision of novel objects to a scientifically informed practice that addresses cognitive, social, and physical welfare needs across species.
Zoo enrichment science has matured substantially from the early days of providing balls and hanging ropes. Modern enrichment programmes are grounded in natural history: a great ape that naturally spends hours foraging needs problem-solving challenges, not just novel objects; a big cat that naturally patrols large territories needs both space and olfactory complexity; a social species kept in an inappropriate social grouping will show stress regardless of physical enrichment provided. The most welfare-positive enrichment programmes address the full behavioural repertoire of the species -- cognitive, social, physical, and sensory -- rather than providing physical novelty as a default.