Seasonal dynamics of agonistic behavior and hormones in an ex situ all-male colony of large flying foxes.

Large flying foxes (Pteropus vampyrus) are a socially complex species. In situ colonies typically comprise thousands of individuals in small harems of one male to many females. In ex situ environments, all-male colonies are becoming more common due to a surplus of males in the population. There is limited information describing the hormonal and behavioral patterns of all-male colonies during the breeding season. We assessed seasonal changes in hormones and behavior in an all-male colony of 12 large flying foxes at Disney's Animal Kingdom . We validated hormone assays using morning urine and fecal samples to assess seasonal changes in excreted immunoreactive testosterone and glucocorticoid metabolites. We collected behavior data using an all-occurrence method, recording agonistic behaviors related to territorial defense (hooking, biting, wing flexing, vocalizing, and wrestling), and sexual behavior (mounting and frontal grabbing). Results indicated that (i) we could reliably measure testosterone and glucocorticoid metabolites concentrations from fecal and urine samples collected from individual bats; (ii) there were distinct relationships between changes in levels of agonism and hormone concentrations throughout the year; and (iii) three agonistic behaviors (chasing, wrestling, and open-mouth threat) peaked prior to the increase in testosterone and glucocorticoid hormones measured during the breeding season. These three behaviors could potentially be used as early indicators to signal the onset of the breeding season and allow time to implement ex situ management changes to reduce the incidence of agonism between individuals.