Behavioral Dynamics of Biparental Negotiation

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Cooperating with others often not does not appear advantageous to all involved parties, yet individuals in many species cooperate in sometimes complex ways. Biparental care offers a model system for experimental analysis of simple cooperation. Two unrelated individuals each contribute to a shared task, but it is not always clear why they do not invest less than they do, especially if that would encourage the partner to invest more. From evolutionary game theory, a 'negotiation model' predicts that reduced effort by one mate should trigger its partner to fill in for the deficit only partially. Tests of this prediction on avian parents provisioning their offspring have produced ambiguous results, perhaps because individuals cannot always monitor how much or how often a mate feeds the young. By contrast, the shared task of incubation seems better-suited for such monitoring because changeovers usually involve face-to-face contact and eggs retain tell-tale warmth. As predicted by negotiation, experimentally-induced reduction of male incubation in house sparrows leads to female partial compensation. Furthermore, the increases in female incubation seem to occur mainly after social interactions with the male. The current project addresses male responses to experimental manipulations of female time-on-eggs, especially whether he adjusts his own incubation or aggression toward her. Females increase incubation time when food is nearby, but reduce it when the eggs are warmed. The investigators have developed an electronic system for supplying artificial heat (at incubation temperature) only when the female is at the nest. Experimental analysis of simple forms of cooperation should improve our understanding of cooperation in general, and of the role of coercion in maintaining cooperation. Close to campus, this project offers outstanding experience and training opportunities to undergraduate and graduate students alike, both in field experimentation and theoretical biology, while being particularly amenable to engaging public interest.