Meeting Abstract

12.2  Thursday, Jan. 3  Chronic Stress in Bridge- and Cave-roosting Brazilian Free-tailed Bats: Assessing Cortisol Response to Hormonal Challenges ALLEN-HRISTOVA, L.C.*; WIDMAIER, E.W.; KUNZ, T.H; Boston University, Boston; Boston University, Boston; Boston University, Boston allenlou@bu.edu

Over the past two decades, the Brazilian free-tailed bat (Tadarida brasiliensis) has increasingly used bridges as roosts in the southern United States. This species roosts in some of the largest aggregations of mammals on earth and occupies a variety of roost types making it an attractive model for the study of stress physiology. However, little research has examined the health of individuals living in man-made structures. It is important to consider how roost characteristics and the pressure of anthropogenic disturbance influence stress physiology in this species. In previous work we found that during pregnancy female free-tailed bats at caves exhibit lower baseline cortisol (CORT) levels than females at bridges. However, this pattern reversed during lactation and post-lactation with females living in bridges having lower baseline CORT levels than females living in caves. Female bats at bridges were also in better body condition than those at caves. We tested the hypothesis that lower baseline CORT levels in bridge bats during lactation and post-lactation are a result of attenuation in CORT production in response to chronic stress. In order to determine if bats exhibit an adaptive stress response as a result of chronic stress and to test the functioning of the HPA-axis we subjected females to Dexamethasone or ACTH, hormonal challenges, followed by assessment of circulating CORT levels. We predicted that if bats living in bridges are chronically stressed they should exhibit a reduced response to both hormonal treatments compared with non-stressed (cave-dwelling) individuals. Results from this work will be discussed in relation to implications concerning the ecology and management of this species.