Effects of testosterone propionate and pituitary-adrenal hormones on the social behaviour of male ducklings (Anas platyrhynchos L.) in two test situations

Glucocorticoid interaction with aggression in non-mammalian vertebrates: reciprocal action

Socially aggressive interaction is stressful, and as such, glucocorticoids are typically secreted during aggressive interaction in a variety of vertebrates, which may both potentiate and inhibit aggression. The behavioral relationship between corticosterone and/or cortisol in non-mammalian (as well as mammalian) vertebrates is dependent on timing, magnitude, context, and coordination of physiological and behavioral responses. Chronically elevated plasma glucocorticoids reliably inhibit aggressive behavior, consistent with an evolutionarily adaptive behavioral strategy among subordinate and submissive individuals. Acute elevation of plasma glucocorticoids may either promote an actively aggressive response via action in specialized local regions of the brain such as the anterior hypothalamus, or is permissive to escalated aggression and/or activity. Although the permissive effect of glucocorticoids on aggression does not suggest an active role for the hormone, the corticosteroids may be necessary for full expression of aggressive behavior, as in the lizard Anolis carolinensis. These effects suggest that short-term stress may generally be best counteracted by an actively aggressive response, at least for socially dominant proactive individuals. An acute and active response may be evolutionarily maladaptive under chronic, uncontrollable and unpredictable circumstances. It appears that subordinate reactive individuals often produce compulsorily chronic responses that inhibit aggression and promote submissive behavior.

Seasonal changes of sexual and territorial behaviour and plasma testosterone levels in male lesser sheathbills (Chionis minor)

Lesser Sheathbills Chionis minor (Aves: Charadriiformes) have a brief annual breeding season but under certain circumstances territoriality persists outside the breeding season. Seasonal increases in plasma testosterone levels in free-living adult males coincided with increases in the mass of tests, the seasonal peak in mutual pair displays and the occurrence of nest-building and copulation. Territorial aggression outsids the breeding season was not dependent on high testosterone levels.