The effect of social learning on the neuroendocrine basis for territorial aggression

Abstract

Effects of hormones on behavior have been recognized for over a century. The reciprocal is also true ­ behavior can have profound effects on hormone secretions. For example, in response to conspecific intruders, testosterone in territorial male birds can increase to maintain aggression over the course of a challenge. Thus, social cues are often powerful stimuli for the induction of neuroendocrine responses. Recognition of competitors can be altered by sexual imprinting ­ birds reared by heterospecifics (cross-fostered birds) often misdirect territorial aggression toward the foster species. However, it is not known whether neuroendocrine responses are misdirected in a similar fashion. The organization of the neuroendocrine system may be pre-programmed to respond only to conspecific cues.

Great tits and blue tits misdirect aggressive responses after cross-fostering. I will examine whether the testosterone response of free-living tits toward heterospecifics becomes similarly misdirected to determine whether the organization of neuroendocrine responses is flexible to early social learning. I hypothesize that early social memory will have a tremendous impact not only on behavior, but also on the structuring of hormonal responses in the brain. Great tits and blue tits are especially well-suited for this proposed research because they show species-specific differences in the degree of sexual imprinting. The behavioral responses of adult cross-fostered males toward conspecific and heterospecific decoys will be investigated with simulated territorial intrusions. Blood from focal birds will then be collected and assayed for testosterone. Birds raised by unrelated conspecifics will serve as controls. These studies will strengthen our understanding of the role of early social cues in the control of neuroendocrine secretions, and will provide a solid basis for future studies of hormone-behavior interactions.

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