Meeting Abstract
Conceptual models suggest that the cost of mounting repeated physiological responses to stressors will depend on both the severity and duration of acute stressors, yet few studies manipulate stressors in a graduated fashion. We studied individual variation in both the response to—and downstream consequences of—repeated exposure to brief spikes in corticosterone. We experimentally induced acute corticosterone spikes on either three or six consecutive days in incubating tree swallows and compared the effects of these treatments to two control groups. Our manipulations were accomplished non-invasively by applying corticosterone dissolved in DMSO gel to an artificial egg so that each dose was absorbed across the female’s brood patch without the need for capture on treatment days. Females in all groups were captured once before treatment and twice post treatment to collect measurements and blood samples. At our capture points, we measured both baseline and stress induced corticosterone concentration as well as the efficacy of negative feedback following injection with dexamethasone. Additionally, we measured glucose mobilization from baseline to 30 minutes post capture and two markers of oxidative metabolism pre- and post treatments. Finally, all nests were equipped with RFID readers and each adult was marked with a PIT tag to record continuous information on parental incubation and provisioning rates before, during, and after treatments. We discuss both the mean effects of our graduated series of acute stressors and the role of individual variation in pre-treatment physiology in determining the downstream behavioral and physiological consequences of repeated exposures to acute and unpredictable physiological stressors.
