Feeding Ecology of Sea Otters in Soft-Bottom Habitats

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Sea otters are unique among all the marine mammals because large foraging fronts are invading historical feeding grounds as the sea otter populations recover and expand their range. This population expansion provides important natural experiments that help to evaluate how otters affect prey populations, non-prey communities and benthic habitats. Although most previous studies of the community role of otters derive from the rocky shore, none have documented these exciting natural experiments and almost nothing is known about the foraging habitats of otters in soft-sediment environments. Oliver proposes to establish long-term studies of how sea otters utilize soft-sediment prey communities, which are primarily dominated by clams. The general approach is to locate active foraging fronts and to establish permanent underwater transects. These transects will be located in old feeding grounds that are heavily exploited, in recently invaded sites that are heavily exploited, in relatively unexploited feeding grounds that will be invaded by otters, and in unexploited areas that are not likely to be used by otters. One such gradient of feeding activity exists around Afognak Strait, by Kodiak Island. Although the quantitative sampling that will be done along existing feeding gradients (foraging fronts) will provide considerable insight into how changes in sea otter populations relate to changes in prey communities, the long-term monitoring of permanent transects is even more important and will provide the most direct evidence for the sea otter's role in structuring soft-sediment communities. This work is closely coordinated with population and behavior studies of sea otters that will be done by the U.S. Fish and Wildlife Service in Alaska. This is a Research in Undergraduate Institutions Award.