P2.172 Thursday, Jan. 5 Seasonal differences in the functioning of the hypothalamus-pituitary-adrenal axis and initial transference to captivity in wild House Sparrows LATTIN, Christine R*; BAUER, Carolyn M.; DE BRUIJN, Robert; ROMERO, L. Michael; Tufts University; Tufts University; Tufts University; Tufts University email@example.com
The hypothalamus-pituitary-adrenal (HPA) axis is essential in helping wild animals cope with environmental challenges. HPA activity is modulated seasonally in many species, and the stress of captivity can interfere with HPA functioning. However, it is not known how these two factors interact–are there particular life history stages when animals are more or less vulnerable to the stress of captivity? We tested this hypothesis by capturing wild House Sparrows during five different seasons: early winter, late winter, pre-breeding, early breeding and late breeding. At each time point, we did a full test of HPA functioning by measuring baseline and stress-induced corticosterone (CORT), negative feedback in response to an injection of dexamethasone, and maximum response through an injection of adrenocorticotropic hormone (ACTH) both before and after 5 days of captivity in the lab. Thirty-nine of the 41 birds lost weight during the 5 days of captivity; mean weight loss was 2.8 g, or ~10% of a sparrow’s total body weight. Across all seasons, sparrows showed an increase in baseline CORT due to the stress of captivity. However, there was an among-season difference in how ACTH challenge was affected by captivity. This seems to be due to a downregulation of the initial response to ACTH in the late summer compared to other seasons, which is then upregulated during the 5 days of captivity. It is possible that these birds are showing an anticipatory downregulation of their response to ACTH in preparation for molt, a time of year encompassing a natural nadir in HPA activity. In any case, these data suggest that birds in the late summer may potentially be more vulnerable to the stress of captivity.