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23 August 2021 Livetrapping is not biased by the endocrine stress response: a preliminary study in the degu (Octodon degus)
Michelle A. Lapointe, Carolyn M. Bauer, Luis A. Ebensperger, J. Michael Reed, L. Michael Romero
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Abstract

While livetrapping is a vital field research tool, it is not a completely unbiased method of sampling. Biased trapping arises during field endocrinological studies whenever hormone levels or response influence the probability of capture of a subject. We repeatedly captured wild, free-living adult degus (Octodon degus) from the same location over 12 days to determine whether individuals with a certain endocrine stress profile were more likely to be captured repeatedly than others. We measured baseline cortisol (CORT), stress-induced CORT, and negative feedback efficacy via a dexamethasone suppression test in adult male and lactating and nonlactating female degus upon initial capture. We successfully recaptured approximately half of the degus. None of the 3 indices of the stress response at initial capture predicted whether a degu would be recaptured. However, baseline CORT levels at 1st capture had a weak, negative relationship with the number of days between 1st and 2nd capture. Because most animals interpret capture and restraint as an acute stressor, we also analyzed the effect of recapture on the endocrine stress response. Baseline and stress-induced CORT concentrations were measured upon each subsequent recapture for up to 5 total captures. Upon subsequent recaptures, neither stress-induced CORT nor baseline CORT changed significantly. Additionally, individual stress-induced and baseline CORT titers were repeatable within our sample population. These findings suggest that livetrapping does not select for animals with certain endocrine stress profiles, and that degus fail to habituate to repeated capture and restraint stress.

Michelle A. Lapointe, Carolyn M. Bauer, Luis A. Ebensperger, J. Michael Reed, and L. Michael Romero "Livetrapping is not biased by the endocrine stress response: a preliminary study in the degu (Octodon degus)," Journal of Mammalogy 96(4), 762-771, (23 August 2021). https://doi.org/10.1093/jmammal/gyv081
Received: 6 December 2014; Accepted: 17 March 2015; Published: 23 August 2021
KEYWORDS
baseline CORT
Cortisol
hypothalamic–pituitary–adrenal axis
livetrapping
negative feedback
Octodon degus
repeatability
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