(Uploaded by Plazi for the Bat Literature Project) The purpose of this study was to determine whether canine wear influences the diet of big brown bats (Eptesicus fuscus). We hypothesized that tooth wear reduces the ability to consume hard-bodied insects, such as beetles, and that older E. fuscus (those with worn canines) would thus include fewer beetles in their diet than younger individuals (those with less-worn canines) do. We examined 600 fecal pellets collected from 60 female bats captured at a single maternity colony in southeastern Alberta, Canada. The diets of two groups were similar in composition, despite considerable differences in canine wear. Diets were dominated by beetles (Coleoptera), which accounted for 30 to 40% of the identifiable food items. Younger bats included more beetles in their diet, although the difference was not statistically significant. The results suggest that older bats are still able to use their worn canines to effectively puncture hard exoskeleton, perhaps because of the angular shape of the worn teeth.