HAHN, Thomas P*; BREUNER, Creagh W; Univ. of California, Davis; Univ. of Texas, Austin: How does the acute adrenocortical stress response relate to fitness?

The acute adrenocortical response to stress presumably has adaptive value to free-living animals, but precisely how it relates to fitness remains uncertain. Field studies focusing on the acute response generally do not make the final connections between inter-individual variation in acute stress response characteristics and inter-individual variation in fitness. Here we attempt a fresh look at the potentially beneficial effects of the acute adrenocortical stress response for free-living animals. We primarily emphasize the need to extend field studies to include comparisons between inter-individual variation in acute stress physiology and direct measures of reproductive success and survival. We present a functional categorization of the processes connecting environmental events to the fitness consequences themselves, via organismal responses and intermediate performance measures. Finally, we emphasize the importance of incorporating stress physiology into long-term field studies that permit quantification of reproductive success and survival. This approach provides insight into: (1) how variation in acute stress response relates to fitness, (2) whether selection is operating on features of stress physiology in populations, and whether that selection is directional or stabilizing, and (3) what constitutes �good� and �bad� stress response features under particular environmental circumstances. Identifying direct connections between acute response and fitness constitutes one of the most important and logical next steps for research on adrenocortical stress physiology.