Sound Use, Sequential Behavior and Ecology of Foraging Bottlenose Dolphins, Tursiops Truncatus
WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
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Odontocetes are assumed to use echolocation for navigation and foraging, but neither of these uses of biosonar has been conclusively demonstrated in free-ranging animals. A new observation platform combining underwater acoustic recording and a remote controlled video camera suspended from a tethered airship allowed me to describe previously unreported foraging behaviors and elucidate functions for behaviors already defined but poorly understood. A single-step transition analysis beginning with prey capture and receding in time identified significant links between observed behaviors and prey capture. Ecological factors affecting the occurrence of specific behaviors and behavioral transitions include mesoscale habitat variation and individual preferences. The role of sound in foraging, especially echolocation is less well understood than the behavioral component. Acoustic recordings revealed that single animals are much more vocal than animals in groups, both overall and during foraging. For single foraging animals, the use of whistles and pops varied significantly by habitat, but echolocation occurred consistently throughout foraging sequences and across habitat types. Acoustic data were also collected with a newly developed tag that recorded all sounds produced by an individual. Low overall click and whistle rates were recorded with both occurring in bouts separated by relatively long periods of silence.