Lambert, H., Elwin, A., D’Cruze, N. 2022. Frog in the well: A review of the scientific literature for evidence of amphibian sentience. Applied Animal Behaviour Science 247, 105559.

Millions of amphibians are traded annually around the world for the exotic pet industry. Their experience during both trade, and in captivity as pets, leads to numerous animal welfare issues. The poor welfare of many pet amphibians is due in part to poor attitudes and acceptance of amphibian species to suffer. Amphibians, like other vertebrate species, are sentient, which means that their feelings matter. In our study, we have sought to explore the scientific literature over 31 years (1990–2020), to establish what aspects of sentience are accepted and still being explored in amphibians. Our review aimed to; 1) assess the extent to which amphibian sentience features in a portion of the scientific literature, 2) to determine which aspects of sentience have been studied in amphibians, and in which species, and 3) to evaluate what this means in terms of their involvement and treatment in the global exotic pet trade. We used 42 keywords to define sentience and used these to search through four databases (ScienceDirect, BioOne, Ingenta Connect, and MDPI), and one open-access journal (PLOS ONE). We recorded studies that either explored or assumed sentience traits in amphibians. We found that amphibians were assumed to be capable of the following emotions and states; stress, pain, distress, suffering, fear, anxiety, excitement, altruism and arousal. The term ‘emotion’ was explored in amphibians with mixed results. Our results show that amphibians are known to feel and experience a range of sentience characteristics and traits and that these feelings are utilised and accepted in studies using amphibians as research models. There is, however, still much more to learn about amphibian sentience, particularly in regards to positive states and emotions, and this growing understanding could be used to make positive changes for the experiences of amphibians in captivity.