Hot and bothered: alterations in faecal glucocorticoid metabolite concentrations of the sungazer lizard, Smaug giganteus, in response to an increase in environmental temperature

Abstract

Despite the commonly held belief that reptiles are immune to extreme temperatures, global warming is predicted to result in the loss of 40 % of all reptile species by 2080. In order to understand the effects of elevated temperature on African reptile physiology and health, additional research is required. We studied the physiological stress response of sungazer lizards (Smaug giganteus) facing elevated temperatures within captivity. Control animals (1M, 2F) were kept at 30 o C throughout the 13-week study period. Test animals (1M, 2F) were exposed to 30 o C for 4 weeks (stage 1), 39 o C for six weeks (stage 2) and 30 o C for 3 weeks (stage 3).Faecal samples were collected from both control and test animals to monitor faecal glucocorticoid metabolite (fGCM) concentrations as a proxy of physiological stress. While the fGCM levels of control females remained constant, test females showed an acute fGCM increase following the increase and subsequent decrease of temperatures. The test male had significantly higher fGCM levels during stage 3 compared to stage 1 and 2. The control male, although displaying constant fGCM levels throughout the study, had higher fGCM levels than the test male. The results indicate that a considerable temporal increase in environmental temperature did not lead to chronically elevated adrenocortical activity in sungazer lizards. It is likely that inherent traits within the species allows the species to adapt to such changes. Furthermore, the endangered status of the species and limited availability of study animals restricted the sample size in this study to a few, captive-based lizards. Therefore, while our results are an important addition to reptile conservation, they should be extrapolated to freeranging populations with caution. Future research should consider the effects of chronically elevated temperature in relation to water and food shortages, as well as inter-individual variation in physiological responses.

Monitoring the stress physiology of free-ranging mugger crocodiles (Crocodylus palustris) across diverse habitats within Central Gujarat, India

“…However, due to the ease of collection, faecal GCM (fGCM) measures have become largely popular. fGCM levels have been measured across diverse groups or taxa, including sungazer (S maug giganteus ) ( Scheun et al. , 2021 ), southern pied babblers ( Turdoides bicolor ) ( Moagi et al.…”