Posture as a Non-Invasive Indicator of Arousal in American Toads (Anaxyrus americanus)

Abstract

Animal welfare has become a priority for modern zoos and aquariums. However, amphibians have not yet been the focus of much welfare research, perhaps in part because they do not tend to display many quantifiable active behaviors. This study focused on nine zoo-housed American toads (Anaxyrus americanus), a species that displays long periods of sedentary behavior, to explore whether more subtle cues could serve as welfare indicators. A novel American toad posture index was developed that characterized toad posture based on the angle of their forelimbs, visibility of ventral regions, and body weight distribution. As an indicator of arousal, approximate breathing rates were assessed based on the rate of expansion of the toads’ throats. Subsequent analyses revealed that lower body postures were associated with slower rates of throat expansion and raised postures with faster rates of throat expansion, suggesting that posture may be a promising way to quickly and non-invasively assess toad arousal. This work lays important groundwork for assessing welfare of an understudied species, and we are optimistic that, with additional validation, these approaches can be applied in future amphibian welfare research.