Stress responses involve the secretion of the glucocorticoid hormones cortisol and corticosterone. These hormones initiate metabolic and behavioural changes that help animals adjust to stressors. Glucocorticoid stress responses have been studied in all vertebrate groups, and plasma glucocorticoid concentrations increase in response to capture, restraint or confinement in all species of animals. Whilst standard deviation or standard error values are always reported alongside mean values, it is only when graphs of individual responses are shown that the extensive variation between individual animals in their responses to the same stressors is readily apparent. Some animals have little or no response to a stressor that evokes a relatively large response in other animals. The factors that lead to this individual variation, and the extent to which this variation is adaptive or non-adaptive, are little known in most animals. Stress responses in different vertebrate groups will be illustrated, with an emphasis on our work on stress responses in birds. The significance of individual variation will be discussed, and opportunities for future studies of glucocorticoid responses in animals that focus on individual responses will be identified.

連絡先：上田　宏　（北海道大学　北方生物圏フィールド科学センター：hueda@fsc.hokudai.ac.jp)