Dissertation Research: Physiological Mediation of an Age-related Life History Trade-off

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Adults are predicted to increase reproductive investment with age. This is thought to occur because as adults age, they necessarily have fewer future reproductive attempts. Several studies support this expectation, however, we currently have little information about the physiological mechanisms mediating this commonly observed pattern. One physiological mechanism that may be important in regulating age-related changes in parental investment is the attenuation of the stress response and decreased sensitivity to elevated glucocorticoid levels. In response to stress, vertebrates release glucocorticoids. Elevated glucocorticoid levels inhibit reproductive behaviors and enhance self-maintenance behaviors. Therefore, adults are predicted to suppress the stress response and to be less behaviorally sensitive to elevated glucocorticoid levels with age. This study will investigate whether changes in the stress response and glucocorticoid sensitivity mediate age-related changes in parental investment in a long-lived seabird, the common tern Sterna hirundo. This research will enhance our understanding of the relationship between stress physiology and age as well as our understanding of the physiological mechanisms mediating age-related life-history trade-offs.Broader Impacts: Undergraduate researchers will be involved in all aspects of this research project. In addition, this research may have important conservation implications. Knowledge about how age influences the stress response may inform wildlife managers about which segments of the population are the most vulnerable to environmental disturbance.