Quantification of thermal preferences can inform issues relevant to applied biology. For instance, many anthropogenic factors can alter the thermal environment posing threats to the performance of organisms. Global climate change, deforestation, or more generally the loss of shading caused by habitat destruction, can greatly increase the temperatures to which organisms are exposed and generally decrease thermal microhabitat variation. Moreover, infectious diseases, many of which are introduced or exacerbated by humans, often induce behavioral fevers (an acute increase in temperature preference in response to pathogen exposure) in ectotherms that can be important for resisting infections and reducing the adverse consequences on hosts. Hence, determining the bounds of thermoregulatory abilities among ectothermic populations will be critical for predicting the impacts of widespread anthropogenic change. However, detecting behavioral fever can be challenging. The evidence for behavioral fever in response to Batrachochytrium dendrobatidis (Bd) has been heavily debated with separate lab and field studies concluding that amphibians do and do not respond to Bd exposure with fever. Here we determine the influence of thermal preferences on host resistance to Bd using inexpensive, efficient, and validated methods we developed for measuring thermoregulatory behavior in the laboratory for extended periods of time.
Results/Conclusions
Our methods for measuring behavioral thermoregulation were sensitive enough to detect consistency in the temperature preference of individuals but variation in temperature preferences among individuals while also allowing us to control for humidity, disturbance, and other confounders. We did not find any evidence to suggest behavioral fever as a response to Bd exposure in any of the five amphibian species tested. However, we did find a relationship between individual temperature preference and Bd growth in vivo within species. We found that cold preferring species had a positive relationship between individual temperature preference and Bd growth while warm preferring species had a negative relationship between individual temperature preference and Bd growth. These results demonstrate how variation in individual level resistance can be driven by inherent temperature preferences, which, provides a mechanism for how microhabitat selection and inherent temperature preferences can drive variation in prevalence within a population.