Evaluating the thermal effects of translocation in a large‐bodied pitviper

Abstract

Acute stressors can be costly, often requiring alteration of normal physiological processes to mitigate their effects. Animal translocation may be a very stressful event and result in a reduced ability to maintain homeostasis. The impacts of translocation on the thermal ecology of ectothermic vertebrates, which may rely on preferred habitats for thermoregulation, are currently unknown. In this study, 22 adult male Northern Pacific rattlesnakes (Crotalus oreganus oreganus) were implanted with automated temperature loggers and radio-tracked. Snakes were assigned to one of three treatments: translocation, handling control, and undisturbed control. Short-distance translocation (SDT) and handling treatments were applied weekly for 6 weeks. Hourly body temperature (Tb ) was recorded during the course of the study. Mean Tb was impacted in a time-dependent fashion, where translocated snakes had lower mean Tb than handled controls during the first week of the study only, especially the first 24 hr after translocation. Separating the dataset into day and night revealed that this effect was localized to Tb variation during the day only. Variance in temperature was not impacted by translocation or handling. Snake body mass and time of year were the major factors influencing the thermal profiles of these rattlesnakes. Thermal ecology in male rattlesnakes is resilient to SDT, suggesting that they quickly resume normal behaviors following repeated bouts of acute capture stress and disturbance of their spatial ecology. This study provides support for SDT as a safe measure for mitigating human-snake interactions and facilitating conservation practices regarding male snakes, which are the most frequently encountered sex.

Stress Ecology of the Pacific Rattlesnakes (Crotalus Oreganus and Crotalus Helleri)

“…The magnitude of elevated baseline CORT in the treatment snakes at sample 2 falls within previously reported baseline levels of free-ranging rattlesnakes, including the sister species C. oreganus (Holding et al 2014;Schuett et al 2004;Lutterschmidt et al 2009, Lind et al 2010. Compared to acute elevation during the stress series, CORT was elevated to a much smaller degree via implants.…”

“…Exogenous CORT treatment has revealed that in female geckos (Hoplodactylus maculatus), heat seeking behavior is increased following treatment (Preest & Cree 2008), while in wall lizards (Podarcis muralis) heat avoidance behavior is observed (Belliure & Clobert 2004). In support of our result, a study on translocated rattlesnakes reported lower mean T b during the week immediately after translocation than controls (Holding, Owen & Taylor 2014), which may be related to differences in circulating CORT, although this was not directly assessed (Holding et al 2014a). Our treatment of CORT in rattlesnakes led to lower T b , suggesting that elevated CORT impacts thermoregulatory behavior and not the reverse, as all snakes experienced similar ambient temperature regimes.…”

“…Rattlesnakes are also resilient to manipulation in the field (Taylor et al 2005;Holding et al 2014), such that observed responses are likely representative of treatment, rather than an effect of researcher presence. This thesis describes how the venoms and several behavioral, ecological, and physiological variables of rattlesnakes are affected, including both laboratory and field studies.…”