The status of Pacific Walrus (Odebenus rosmarus divergens) foraging habitat and diet around St. Lawrence Island

Abstract

With ongoing climate change, food resources may be reduced for Pacific walruses (Odobenus rosmarus divergens). Significant differences in walrus foraging habitat (benthic communities) or diet might indicate changes in prey quality or quantity. In this study, benthic infaunal biomass, abundance, and composition were compared between 1970-1974 and 2006 at stations southwest of St. Lawrence Island. Sediment grain size was compared because it strongly determines benthic community structure. Wet weights, counts, and species composition of prey items found in stomachs of walruses collected near the island were compared between the 1980s and 2007. Benthic invertebrate biomass and abundance increased mainly due to high Nuculidae biomass and abundance, although results may be skewed by low sample size. Silt fractions increased regionally. No significant dietary differences were detected in walruses. Walruses may have undergone a population redistribution or decline in response to benthic community changes that would be undetected in stomach content analyses.