The role of acoustic communication in the foraging success of bowhead whales
Arctic Research Initiative
2007 Funded Project
The ecology of bowhead whales (Balaena mysticetus) is closely associated with Arctic sea ice, and continuing changes in summertime ice conditions due to Arctic warming will undoubtedly affect bowhead whale foraging behavior. Baleen whales have been hypothesized to use acoustic communication to cooperatively find and exploit food resources, but obtaining simultaneous observations of vocalizations and foraging behavior have been difficult to obtain. If bowhead whales use acoustic communication to cooperatively forage, then changes in sea ice conditions may make those communications more difficult. As sea ice retreats and open-water prey resources become more widely distributed, bowheads are expected to increase their range over the continental shelf, thus increasing the distance between individual whales. Coordinated foraging via acoustic communication over these longer distances may be more difficult, resulting in reduced foraging success. Moreover, as the extent of open water increases, industrial activities such as oil and gas development, shipping, and commercial fisheries, are anticipated to increase. In addition to posing direct threats to whales via ship strikes and fishing gear entanglements, these activities will likely increase ambient noise levels, making acoustic communication more difficult for the whales.
In August 2007, we will begin a federally sponsored, interdisciplinary research project on bowhead whale feeding ecology that will include a study of foraging behavior. We will deploy suction-cup attached archival tags to bowhead whales to monitor their diving behavior while simultaneously measuring oceanographic conditions and prey distribution with a profiling instrument package. We plan to augment this study with ARI-sponsored deployments of an array of small hand-deployed buoys designed to (1) track the movements of the tagged whale in three dimensions in real time and (2) record and localize the calls of the tagged whale and other whales inside and near the buoy array. With these observations, we will be able to directly assess the foraging behavior of the tagged whale as well as its response to the vocalization behavior of nearby whales (within a few kilometers). We will test the hypothesis that bowhead whales use acoustic communication to cooperatively find and exploit prey resources. The study will provide baseline observations that can be used in the future to study the affect of changes in sea ice, oceanographic conditions, prey distribution, and ambient noise on bowhead whales, an important top predator in the Arctic ecosystem.