ECOLOGICAL BASES OF HORMONE-BEHAVIOR INTERACTIONS - THE EMERGENCY LIFE-HISTORY STAGE

Superimposed upon seasonal changes in morphology, physiology and behav ior, are facultative responses to unpredictable events known as labile (i.e., short-lived) perturbation factors (LPFs). These responses incl ude behavioral and physiological changes that enhance survival and col lectively make up the ''emergency'' life history stage. There is consi derable evidence that glucocorticosteroids, and other hormones in the hypothalamo-pituitary-adrenal (HPA) cascade, initiate and orchestrate the emergency life history stage within minutes to hours. This stage h as a number of sub-stages that promote survival and avoid potential de leterious effects of stress that may result from chronically elevated levels of circulating glucocorticosteroids over days and weeks. These sub-stages may include: redirection of behavior from a normal Life his tory stage to increased foraging, irruptive-type migration during the day, enhanced restfulness at night, and elevated gluconeogenesis. Once the perturbation passes, glucocorticosteroids may also promote recove ry. Additional evidence from birds indicates that glucocorticosteroid responses to a standardized capture, handling and restraint protocol a re modulated both on seasonal and individual levels. Field work reveal s that these changes in responsiveness to LPFs have ecological bases, such as reproductive state, body condition etc., that in turn indicate different hormonal control mechanisms in the HPA cascade.