Does my bum look big in this enclosure? Associations of behaviour and physiology on body mass gain in the woylie (Bettongia penicillata ogilbyi) post-translocation

An individual’s temperament can affect its fitness and survival by influencing behaviours associated with predator avoidance, interactions with conspecifics, refuge selection and foraging. Furthermore, temperament can determine an individual’s response to novel stimuli and environmental challenges, such as those experienced through translocation. Increasing our understanding of the effect of temperament on fitness post-translocation is thus necessary for improving translocation outcomes. This study focused on the woylie (Bettongia penicillata ogilbyi) and, specifically, investigated the influence of individuals’ temperament – determined through measures of behaviour and physiology – on change in body mass post-translocation. Forty woylies were translocated from two predator-free exclosures to a larger exclosure at Mt Gibson Wildlife Sanctuary, near Wubin, Western Australia. Behavioural and physiological measures were recorded during trapping, processing, holding and release, and again ~5 months post-release. In the absence of predation, 100% survivorship of translocated individuals, and extremely high fecundity, body mass was used as a proxy for survival rate. On initial capture (‘pre-translocation’), males had significantly higher faecal corticosterone levels than did females; however, at post-release recapture (‘post-translocation’), there was no significant difference. There was no significant difference in body mass between males and females pre-translocation; however, post-translocation, females had gained significantly more body mass than had males. Combined analyses of behavioural and physiological variables showed that the strongest predictors of body mass gain were sex, heart rate lability and a measure of escape behaviour when released (a convoluted escape path). Most behavioural measures were not consistent or repeatable and hence, individual temperament could not be determined. However, it is also possible that the translocation was not sufficiently challenging for individuals to be able to test differences in temperament. Future research could involve similar trials on animals that are released into unfenced settings. More robust behavioural measures that can be easily incorporated into the translocation process without increasing stress or affecting welfare of individuals should also be trialled. On average, all woylies recaptured had increased in body mass, suggesting that, in the absence of predation, the selected candidates were able to cope with the stress of translocation, and also possessed the behavioural plasticity to successfully find resources and adapt to a novel environment