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Indirect fitness benefits from kin selection can explain why non-breeding individuals help raise the young of relatives. However, the evolution of helping by non-relatives requires direct fitness benefits, for example via group augmentation. Here, we examine nest visit rates, load sizes and prey types delivered by breeding pairs and their helpers in the(More)
Kin selection predicts that helpers in cooperative systems should preferentially aid relatives to maximize fitness. In family-based groups, this can be accomplished simply by assisting all group members. In more complex societies, where large numbers of kin and non-kin regularly interact, more sophisticated kin-recognition mechanisms are needed. Bell miners(More)
We studied a population of rufous whistlers, Pachycephala rufiventris, throughout a single breeding season in central New South Wales, Australia. We evaluated the relation between plasma testosterone (T) and reproductive behaviors using both simulated territorial intrusions (STIs) and subcutaneous T implants. We compared circulating T values to aggression(More)
OBJECTIVE The goal of this study was to evaluate how black and white men and women responded physiologically to specific laboratory challenges. METHODS Hemodynamic responses to an active coping (evaluated speaking) and two inhibitory-passive coping (mirror tracing, cold pressor) tasks were examined in 138 black and white men and women. RESULTS(More)