The effects of exogenous testosterone on male Northern Mockingbirds during the breeding season

摘要

The challenge hypothesis (Wingfield et al. 1990) states that a positive correlation between plasma testosterone (T) and aggression occurs only under conditions of social instability, that is, when access to resources is being persistently challenged in contests over territory borders or position in a dominance hierarchy. Sizeable increases in plasma T levels above a relatively low breeding-season baseline are produced by intermale aggression and female sexual activity, while male parental care is associated with lower T levels. The hypothesis accounts for fluctuations in breeding-season levels of plasma T in numerous temperate avian species (Wingfield et al. 1990).