Philosophy of environmental enrichment: past, present, and future

Mellen and MacPhee reflected on how environmental enrichment evolved from ad hoc novelty provision toward a goal-directed, integrated husbandry process. They proposed a framework in which enrichment is set, planned, implemented and evaluated as part of routine animal care, tied to specific behavioural goals and assessed with data. The paper argued enrichment should be a continuous management cycle rather than a collection of toys, and that it must be documented and refined over time. Widely cited across zoo biology, it shaped the now-standard SPIDER framework for enrichment programs and influenced how felid and other carnivore enrichment is designed, justified and measured in accredited institutions.