Chimpanzees were widely used in biomedical research until welfare and ethical arguments drove near-complete phase-out in developed countries.
Research chimpanzees experienced invasive procedures, social isolation, and psychological trauma. Post-research life in sanctuaries reveals the depth of trauma through behavioral stereotypies and social difficulties. The phase-out of chimpanzee research demonstrates that ethical arguments can drive scientific practice change even when alternatives are imperfect. The welfare lesson applies to research on all great apes.