Do “Prey Species” Hide Their Pain? Implications for Ethical Care and Use of Laboratory Animals

Abstract Accurate pain evaluation is essential for ethical review of laboratory animal use. Warnings that “prey species hide their pain,” encourage careful accurate pain assessment. In this article, I review relevant literature on prey species’ pain manifestation through the lens of the applied ethics of animal welfare oversight. If dogs are the species whose pain is most reliably diagnosed, I argue that it is not their diet as predator or prey but rather because dogs and humans can develop trusting relationships and because people invest time and effort in canine pain diagnosis. Pain diagnosis for all animals may improve when humans foster a trusting relationship with animals and invest time into multimodal pain evaluations. Where this is not practical, as with large cohorts of laboratory mice, committees must regard with skepticism assurances that animals “appear” pain-free on experiments, requiring thorough literature searches and sophisticated pain assessments during pilot work.