Heart rate and behavior are regulated independently of corticosterone following diverse acute stressors

Abstract

Captive European starlings ( Sturnus vulgaris) were subjected to five acute stressors: a visual stressor (strobe light), an auditory stressor (music), and disturbance by three different humans; their accustomed caretaker, an antagonist (the experimenter), and a novel human. Heart rate (HR), behavioral, and corticosterone (CORT) responses to each stressor were simultaneously recorded. The visual stressor elicited a significantly lower maximal HR response [∼550 beats per minute (bpm)] that returned to basal levels (335 bpm) more quickly than the HR increases elicited by any of the four other stressors (∼700 bpm). These data suggest that the degree of novelty may alter the magnitude and duration of the HR response. Behaviorally, both the auditory stressor and the human antagonist caused a significant decrease in preening behavior without subsequent increases in activity, beak wiping (a behavioral indicator of displaced aggression), or bouts of feeding and/or drinking. In contrast to the stressor-specific differences in HR and behavior, all five acute stressors elicited similar sub-maximal CORT responses, suggesting the presence of a standardized CORT response to sudden, acute stimuli in wild captive starlings. The data indicate that starlings modulate HR, CORT, and behavioral responses depending upon the stressor, but that these three pathways are regulated independently.