Amphibians

Amphibian species such as frogs, toads, and salamanders are commonly used in laboratory animal research settings, but there is no objective means to assess the presence and severity of pain in amphibians, especially since they do not exhibit any facial expression. However, research studies have shown that amphibians are able and motivated to learn to avoid noxious stimuli.

Some exotic animal clinicians use nonspecific clinical signs such as decrease in avoidance movement (e.g., when approached by a handler) or decrease in appetite as indicators of pain in these animals.