Meeting Abstract

P2.112  Jan. 5  Seasonal and roost type variation in baseline and stress-induced cortisol levels in the Brazilian free-tailed bat (Tadarida brasiliensis) ALLEN, L. C.*; WIDMAIER, E. P.; KUNZ, T. H.; Boston University; Boston University; Boston University allenlou@bu.edu

The Brazilian free-tailed bat (Tadarida brasiliensis) possesses characteristics that make it an attractive model for the study of stress physiology. This bat roosts in some of the largest aggregations of mammals on earth and occupies a variety of roost types. Roosts are likely to differ in quality, due to variation in temperature or thermal stability, colony size and levels of disturbance. It is interesting to consider how these characteristics and the competing biological needs of individuals will influence physiological function in this species. This study examines variations in glucocorticoids specifically baseline and stress-responsive cortisol levels, in adult female Brazilian free-tailed bats. We captured and examined females from late-May until early-October at four different sites (two caves and two bridges) in south-central Texas in order to test the hypotheses that cortisol levels would 1) vary over the season with reproductive stage and 2) differ between site types. Our results indicate that variation in cortisol levels are correlated with reproductive status, body condition and site type. Pregnant females exhibit higher baseline and stress-induced cortisol levels than lactating, post-lactating and non-reproductive females. Excluding pregnant females, bats with lower mass to forearm length ratios (i.e. body condition) also showed higher baseline cortisol levels than heavier bats. Furthermore, individuals living in bridges tend to have lower baseline cortisol levels than bats roosting in caves. Our findings are important for determining the health of colonies subjected to different potential levels of stress, and the suitability of bridges as alternate roosts for this species.