How veterinarians and researchers measure pain in animals, what tools and scales are used, and why pain assessment matters for welfare.
Accurate pain assessment in animals is foundational to welfare because pain that is not detected cannot be treated. The challenge is that animals communicate pain through behavioral and physiological changes rather than verbal reports, and these signals can be subtle or masked by prey-species stoicism. Validated pain assessment tools have been developed for companion animals, laboratory animals, and increasingly for farm animals. Grimace scales, which measure facial action units associated with pain, have proven particularly useful and scalable. Despite advances in pain assessment, undertreatment of animal pain remains widespread in both companion animal medicine and farm animal management.