Feeding ecology and morphology of the upper canines in bears (carnivora: Ursidae).

The morphology and mechanical strength of the upper canines in all eight extant species of ursids is analyzed, and the findings are discussed in relation to feeding ecology. Ursids have proportionally smaller canines than other large carnivores with a specialized feeding ecology, such as large felids, and the upper canine morphology is both canid-like and felid-like. The giant panda is the most divergent species, and its short, blunt, and cone-like canines appear well adapted for tearing into bamboo. The almost equally herbivorous spectacled bear has a less derived canine morphology. The large canines of the sun bear are divergent from other ursine ursids, and may be an adaptation for tearing open tree trunks in search of insects. Discriminant Analysis is successful in separating ursid species on the basis of canine morphology, but the canines of ursine ursids, and also of the spectacled bear, show greater resemblance among the species than the marked differences in feeding ecology would suggest. This could be in part due to a short evolutionary history, and in part due to canines not having been subjected to much evolutionary selection as has been the case among other large carnivores, such as large felids. Ursids are probably evolutionarily and ecologically successful due to physical size and strength rather than a derived craniodental anatomy.