Meeting Abstract
Corticosterone (CORT) levels are often used as metrics to assess population status and health of wild vertebrates, without an understanding of the effects that elevated CORT levels can induce in a given organism, population, or species. Studies that have attempted to assess effects of CORT often employ multiple-exposure acute stressors as a proxy for chronic stress, without sustained elevation of baseline CORT. We assessed the use of CORT implants as a tool for evaluating effects of chronically elevated plasma CORT in a free-ranging ectotherm so that we could study the effects of chronically elevated CORT in an arid-adapted species that regularly experiences periods of drought and sparse prey availability. We demonstrate that CORT implants can be used to successfully elevate plasma CORT compared to a control group in a population of free-ranging Southern Pacific rattlesnakes (Crotalus helleri) for up to 15 days. Implantation with CORT did not affect plasma osmolality, testosterone, or defensive behavior. Interestingly, we observed increased defensive behavior with higher plasma T and in snakes with more stable daily body temperatures. Trends for higher magnitude of stress response due to lower baseline CORT and increases in body temperature between baseline and stressed samples were observed, regardless of treatment group. These results add to a paucity of literature on effects of CORT on free-ranging terrestrial ectotherms, and suggest that CORT may not greatly influence physiological and behavioral trait expression in arid-adapted ectotherms such as rattlesnakes.
