DIETARY BEHAVIOR OF POLAR BEARS (URSUS MARITIMUS) DURING PREHISTORIC AND HISTORIC TIMES IN ALASKA AS REVEALED FROM DENTAL MICROWEAR TEXTURES

Spatiotemporal recession of sea ice and lengthened melt seasons in the Arctic have resulted in range contraction and body condition declines for regional populations of polar bears (Ursus maritimus). A clearer understanding of polar bear dietary ecology, particularly carcass-utilization, may give insight into adaptive strategies in the face of global climate change, as energy-dense marine resources become increasingly inaccessible to the hypercarnivore specialist. In this study, we use dental microwear texture analysis (DMTA) to compare the textural properties of food consumed by Alaskan polar bears from approximately 1000+ years before present to specimens acquired during the end of the 19^th century and beginning to middle of the 20^th century. Specifically, we tested the hypothesis that carcass utilization increased with an inferred decline in prey availability brought on by increased warming and the reduction of sea ice—which is critical for hunting of marine mammals. DMTA was conducted on the grinding facets of molars known to record dietary information and analyzed via scale-sensitive fractal analysis. DMTA attribute values of the archaeological and modern specimens, including anisotropy (epLsar) and complexity (Asfc) are indistinguishable statistically (all p-values are greater than 0.05). Complexity is useful in distinguishing between carnivorans (including ursids) that consume hard versus soft food items, yet shows no difference in mean attribute values between archaeological and modern polar bears. These data also demonstrate the absence of hard-object feeding (e.g., carcasses) in Alaska, in contrast to an earlier study, but in agreement with finite element analysis which suggests that polar bears are not mechanically suited to consume hard foods like bone. Polar bears have reduced molar dentition when compared to their close relative, the omnivorous brown bear (Ursus arctos), and may be less able to alter their dietary behavior (e.g., more fully exploit carcasses or eat other mechanically challenging resources) with changing climates. Future work is needed to expand our historical samples to include specimens from the 21^st century.