The diet of polar bears (Ursus maritimus) from Svalbard, Norway, inferred from scat analysis

Polar bears (Ursus maritimus) are heavily dependent on marine prey, in particular ice-associated seals, which they hunt on landfast sea ice or free-floating pack ice. Dramatic current (and predicted) losses of sea ice habitat make it increasingly important to gain more knowledge of the relative use by bears of all types of prey from the marine food web as well as from terrestrial sources. This study uses frequency of occurrence of food items in 119 polar bear scats sampled on the sea ice as well as on shore in coastal areas in the Svalbard Archipelago, mainly in spring, between 2003 and 2010 to explore the diet of bears in the region. Ringed seals (Pusa hispida) occurred in 62.2 % (CI 52.8-70.9 %) of the scat samples examined. Various terrestrial plants (32.8 %, CI 24.4-42.0 %) and marine algae (21.8 %, CI 14.8-30.4 %) also occurred frequently in the scats; the significance of this high occurrence of plants and algae is not clear. Bearded seals (Erignathus barbatus) and various bird species constituted only minor components of the diet, while Svalbard reindeer (Rangifer tarandus platyrhynchus) occurred in 9.2 % (CI 4.7-15.9 %) of the scats, indicating that this species may play a more important role than previously reported. The novel combination of genetic analyses of material in the fecal samples along with detailed exploration of the physical-structural properties of prey hairs and plant parts provided a much fuller picture of the diet of polar bears than would have been possible from observational studies of polar bear predation behavior alone. This approach may provide an important tool for monitoring the responses of polar bears to ongoing ecosystem changes that will result from continued warming in the Arctic.