Abstract. I will discuss food-sharing vampire bats as a model system for understanding the development and regulation of long-term cooperative relationships. I first review observational and experimental evidence that vampire bat food sharing is enforced by both nepotism and reciprocity in the broad sense. Second, I ask: why should individuals invest in cooperative relationships with nonkin when kin are available? One explanation is that a kin-limited support network is too small and risky. Investing in a higher quantity of social ties at the expense of relationship quality (“social bet-hedging”) can reduce the risks posed by unpredictable social environments. As predicted by the social bet-hedging hypothesis, I show how experimental removal of key food donors revealed the hidden importance of weak nonkin bonds. Third, I ask: how does a new cooperative relationship develop between complete strangers? One important but untested theory is that individuals develop new cooperative relationships by ‘raising the stakes’: gradually increasing low-cost investments to decide on whether to make higher-cost investments. This behavior has been demonstrated in human strangers playing cooperative games but not in a more ecologically realistic setting. By tracking the development of cooperative relationships between previously unfamiliar wild-caught vampire bats, I show that unfamiliar females selectively escalate low-cost investments in allogrooming to develop higher-cost reciprocal food-sharing relationships. I also discuss current work on social foraging by tracking vampire bat social networks in the wild at fine temporal resolution.
Collins Conference Room
Gerald Carter (The Ohio State University)
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