Meeting Abstract
Wild birds are brought into captivity for conservation purposes such as captive breeding and translocation. Additionally, many studies of avian physiology and behavior are conducted on wild birds housed in the lab. In this study, we sought to better understand differences between wild and captive birds by capturing house sparrows (n=20) and examining body mass, several behaviors, and tissue volumes of heart, fat, spleen, pectoralis muscle and testes immediately after capture and after 2 weeks in the lab. We used computed tomography (CT) imaging with a novel gadolinium contrast agent to assess tissue volumes. To reduce circulating corticosterone, half the birds received mitotane injections (180 mg/kg) every other day; the other half received a vehicle control. After two weeks of injections, mitotane-treated birds had ~50% decreased stress-induced corticosterone concentrations compared to controls. Regardless of treatment, all birds lost ~8% body mass in the first week, and this mass loss persisted through the second week. Fat volume increased, and heart and testes volumes decreased, over the two weeks of captivity in all birds independent of treatment. However, beak-wiping behavior, which can indicate aggression, increased over the two weeks of captivity in control birds only. This study demonstrates that rapid changes in body composition occur in wild birds upon transfer to the lab. Specifically, the significant decrease in heart volume after just two weeks suggests that captive birds may have reduced aerobic capacity compared to wild birds, which could potentially affect their ability to survive if released. Also, our data suggest that experimentally reducing circulating corticosterone may mitigate some captivity-induced behavioral changes.
