Inter- and intra-specific variation in hair cortisol concentrations of Neotropical bats

Abstract

Quantifying hair cortisol has become popular in wildlife ecology for its practical advantages for evaluating stress. Before hair cortisol levels can be reliably interpreted, however, it is key to first understand the intrinsic factors explaining intra- and inter-specific variation. Bats are an ecologically diverse group of mammals that allow studying such variation. Given that many bat species are threatened or have declining populations in parts of their range, minimally invasive tools for monitoring colony health and identifying cryptic stressors are needed to efficiently direct conservation efforts. Here we describe intra- and inter-specific sources of variation in hair cortisol levels in 18 Neotropical bat species from Belize and Mexico. We found that fecundity is an important ecological trait explaining inter-specific variation in bat hair cortisol. Other ecological variables such as colony size, roost durability and basal metabolic rate did not explain hair cortisol variation among species. At the individual level, females exhibited higher hair cortisol levels than males and the effect of body mass varied among species. Overall, our findings help validate and accurately apply hair cortisol as a monitoring tool in free-ranging bats.

Technical validation and a comparison of two methods to quantify individual levels of glucocorticoids in Alpine marmot hair

“…grey wolves Canis lupus [7] whereas other studies reveal higher HCG levels in one sex e.g. vampire bats Desmodus rotundus [51] . Inter-specific variation in factors modifying HC levels may be attributed to inherent physiological differences across the species, or, alternatively confounding impacts of study design such as extraction methods [24] .…”

“…Inter-individual variation in HC measured in our study, while not attributable to age or sex, would have reflected differences in factors known to modulate HC in other species such as social environment [11] , human intervention [12] , social rank [47] , amount of aggression received [58] , temperament [38] , body condition [51] , health [46] or reproductive status [23] all of which warrant further investigation in our species.…”

Advances in understanding bat infection dynamics across biological scales

“…blood, < 5 µl) and non-invasive (e.g. faeces, urine and fur) methods to quantify GCs are increasingly available [ 22 , 23 ].…”