Scientific approaches to enrichment and stereotypies in zoo animals

Swaisgood and Shepherdson reviewed how rigorously zoos had studied enrichment and stereotypy, surveying the published literature for methodological quality. They found many anecdotal claims but a growing body of controlled studies, and proposed a hypothesis-driven framework linking enrichment to specific behavioural and physiological outcomes. They emphasised measuring effect sizes, controlling for confounds, and distinguishing enrichment that reduces stereotypy from enrichment that improves welfare more broadly. The paper became a methodological touchstone, encouraging the field to move from showing that animals use novel objects to demonstrating measurable welfare gains. For carnivore and felid programs it provided a template for designing enrichment trials with proper baselines, controls and quantitative behavioural sampling.