Transport and release procedures in reintroduction programs: stress and survival in grey partridges

Abstract

During translocations, stress, as measured by the increase of glucocorticoids, cannot be avoided, but has been suspected to exacerbate the vulnerability to many causes of mortality after release. Therefore, measures to reduce stress have been proposed, such as keeping animals in pens before release (soft release). In this study, we investigated two open questions in translocations: (1) whether stress caused by the translocation procedure has an effect on survival; (2) whether soft release allows recovering from stress induced by capture and transportation. Hand-raised grey partridges showed a moderate adrenocortical response to transportation and kept the capacity to mount a stress response to a new acute stressor, partly by a decrease of corticosteroid-binding globulin capacity. In contrast to studies demonstrating a pervasive effect of capture and transport by virtual elimination of a proper stress response, we demonstrated a robust stress response and a return of baseline levels to pre-transport levels after 33 h of acclimatization.Possibly captive-bred birds may be less sensitive to capture and transportation than wild-caught birds. During the first month after release, birds held 33 h in release pens survived better when their corticosterone levels were lower. However, survival beyond the first month did not differ between birds held 9 or 33 h in acclimatization pens. Elevated glucocorticoids, as induced by the translocation procedure, likely affect short-term survival after release. We recommend glucocorticoid stress levels be surveyed in an appropriate subsample and minimized during translocations.

Ameliorating transport-related stress in endangered Kemp’s ridley sea turtles (Lepidochelys kempii) with a recovery period in saltwater pools

“…However, prolonged or repeated stress responses have negative long-term effects including suppression of growth in juveniles, increased vulnerability to disease, increased wound-healing time, impaired reproduction, decreased ability to mount a new stress response for any new stressors and long-term alterations in behavior (reviewed in Romero and Wingfield, 2015). In wildlife released to the wild immediately after transportation (‘hard release’), immediate impacts can include an increased tendency to abandon the release site, increased vulnerability to predators and disease and concomitant increased risk of mortality (Jenni et al , 2015). Long-term effects of stress can last months to years, including persistent effects on growth, adult body size, adult behavior and adult reproduction (Romero and Wingfield, 2015).…”

“…Though such impacts of stress have not been assessed in chelonians, these patterns occur in almost all vertebrate taxa that have been studied (Romero and Wingfield, 2015), suggesting caution when exposing wildlife to stress. Therefore, though some stress is clearly inevitable when transporting wildlife, it has been recommended that transport practices be adjusted to minimize and/or ameliorate stress where feasible, especially those transports that occur immediately prior to release (Grandin, 2007; Teixeira et al , 2007; Dickens et al , 2010; Jenni et al , 2015).…”

“…However, given the potential short- and long-term impacts described earlier, it is worth exploring methods to ameliorate transport-related stress in sea turtles. An increasingly common management option employed with other species is ‘soft release,’ holding animals in the vicinity of the release site for some period of time just after transport and before release into the wild (Jenni et al , 2015). For sea turtles, soft releases could involve placement in saltwater tanks or pools near the release site, which, although not fully mimicking conditions in the wild, might at least ameliorate some of the physiological stress caused by transportation.…”

Using Bayesian mark-recapture modelling to quantify the strength and duration of post-release effects in reintroduced populations

“…These threats include Allee effects and demographic stochasticity, both of which are a function of small initial population sizes (Deredec and Courchamp, 2007). However, the biggest threat may be stresses associated with the translocation process (Maran et al, 2009;Dickens et al, 2010;Jenni et al, 2014) or subsequent acclimation to the reintroduction area (Moorhouse et al, 2009;Hamilton et al, 2010;Jachowski et al, 2011;Mihoub et al, 2011).…”

The effect of pre‐release captivity on the stress physiology of a reintroduced population of wild eastern bettongs

“…In the absence of empirical evidence of the physiological effects, conclusions are often drawn from indirect proxies including survival, body‐condition and reproductive activity (e.g. Jenni et al ., ; Richardson et al ., ).…”