Communication and Cooperation

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This research aims to determine the function and information content of communication vocalizations of a large, omnivorous bat, the greater spear-nosed bat. The rich vocal repertoire, unusual social system in which unrelated females form long- lasting groups, and proclivity to forage in groups while producing loud, audible calls make this bat ideally suited for study. Dr. Wilkinson's research is designed to determine if vocal advertisement and group foraging result in reciprocated or mutualistic benefits. To discriminate between these alternatives, he will use infrared-sensitive video and computerized recording equipment to conduct observations and playback experiments on individually marked bats departing from cave roosts or foraging in groups during three months of field work in Trinidad, West Indies. Acoustic analysis of bat vocalizations recorded in the field from known individuals will be used to indicate the type of information that could be contained in particular calls. Behavioral experiments designed to measure the energetic benefits of group foraging and information exchange, as well as the mechanism by which information is transferred, will be conducted on captive bats at the National Zoo, Washington, D.C., over a seven-month period. Reciprocal information exchange is common in all human societies but is unknown for other vertebrates with the possible exception of chimpanzees and dolphins. This research should, therefore, add to our understanding of communication and cooperation in bats and provide insight into the evolution of cooperative communication. In addition, because this bat pollinates flowers and disperses seeds from a variety of tropical trees, an improved understanding of its foraging behavior may provide valuable information for conserving Latin American rain forests.