The behavioral and physiological effects of long-distance translocation on Western Rattlesnakes (Crotalus oreganus)

Abstract

Kory Hayden HeikenLong-distance translocation (LDT), the relocation of an animal outside of its home range, is a popular strategy for mitigating conflict between humans and venomous snakes. While LDT has been demonstrated to prevent a snake's return to the location of capture, it may result in increased mortality, magnitude and frequency of movements, and activity range sizes. Thus, it has generally been discouraged. However, the effects of LDT on stress physiology and thermoregulation have gone largely unstudied in reptiles.To elucidate these effects, we conducted an experimental LDT on Western Rattlesnakes (Crotalus oreganus) on Vandenberg Air Force base in California.Fourteen snakes were monitored, beginning in mid July 2012 and ending in early September. Each was implanted with a radio transmitter and iButton temperature data logger within the coelomic cavity. In late August, seven snakes were translocated to similar habitat, approximately 30 kilometers away, where they were monitored for 9-13 days. Prior to translocation, all snakes were tracked every other day, while after translocation all snakes were tracked every day. A 'Before-After Control-Impact' (BACI) experimental design was used, with a dedicated control group, but also with the translocated group serving as control prior to the act of translocation.We collected data on snake body temperatures (T b ) and temperatures (T e ) of physical operative temperature models (OTMs) that simulated non-thermoregulating snakes and allowed for a comparison of habitat thermal quality between our two study sites. Together, T b and T e allowed for a formal assessment of thermoregulatory effectiveness. Additionally, blood concentrations of corticosterone (CORT), the primary stress hormone in reptiles, and testosterone (T), a metric of male reproductive ability that is often negatively associated with CORT, were assayed just prior to translocation and again at the end of the study. During each of the two sampling periods, in addition to baseline hormone concentrations, stressed hormone concentrations were assayed following the application of an acute stressor (the baseline blood draw plus one hour's captivity in a plastic bucket). We also studied the effect of LDT on the CORT and T response (stressed concentration minus baseline concentration). Furthermore, we evaluated how LDT impacted a suite of behaviors related to defense and movement, as well as snake body mass and body condition index (BCI). Finally, we assessed the effects of LDT on movements and spatial use (activity range size). We sought to assess the effects of LDT on movements, spatial use, and behavior in order to facilitate comparison with other translocation studies, as well as to evaluate those impacts in a physiological context. In addition to assessing the impact of LDT on CORT and T separately, we v evaluated a relationship between the two steroid hormones, and, using a model selection approach, we evaluated relationships between CORT and T and movements and spatial use.The thermal quality of the h...

Moving house: long-term dynamics of corticosterone secretion are unaltered in translocated populations of a rare reptile (the tuatara,Sphenodon punctatus)

“…(2012) found that baseline CORT in desert tortoises ( Gopherus agassizii ) was similar between translocated and control groups at both 1 and 2 years post-translocation, and both Holding et al . (2014) and Heiken (2013) found that baseline CORT and the CORT response in translocated northern pacific rattlesnakes ( Crotalus oreganus ) were not altered post-translocation, compared with controls. In contrast, Gerber et al .…”

Diversity of Snake Rescued From Residential Areas in Greater Jakarta Metropolitan Area, Indonesia

“…in Crotalus spp., Viperidae) and increase the risk of snake death (Reinert and Rupert 1999). In research on Notechis scutatus and Crotalus oreganus, translocation affects the behavior and spatial ecology of snakes by expanding the range and increasing movement (Heiken 2013). This will be a new problem if the snake is released in the forest that is still close to settlements.…”

“…This will be a new problem if the snake is released in the forest that is still close to settlements. However, Heiken (2013) states that longdistance translocation in Crotalus oreganus does not indicate chronic stress or disruption of thermoregulation. It is likely that each species has a different response to translocation.…”