Diet of spotted bats (Euderma maculatum) in Arizona as indicated by fecal analysis and stable isotopes

We assessed diet of spotted bats (Euderma maculatum (J.A. Allen, 1891)) by visual analysis of bat feces and stable carbon (delta C-13) and nitrogen (delta N-15) isotope analysis of bat feces, wing, hair, and insect prey. We collected 33 fecal samples from spotted bats and trapped 3755 insects where bats foraged. Lepidopterans averaged 99.6% of feces by volume; other insects were not a major component of diet. The delta C-13 and delta N-15 values of bat feces were similar to those of moths from families Noctuidae (N), Lasiocampidae (L), and Geometridae (G), but differed from Arctiidae (A) and Sphingidae (S). We used a mixing model to reconstruct diet; three families (N, L, G) represented the majority (88%-100%) of the diet with A + S representing 0%-12%. Although we compared delta C-13 and delta N-15 values of wing, hair, and feces of spotted bats, feces best represented recent diet; wing and hair were more enriched than feces by 3 parts per thousand and 6 parts per thousand, respectively. This pattern was consistent with that reported for other bat species. We suggest that spotted bats persist across a wide latitudinal gradient partly because they can forage on a variety of noctuid, geometrid, and lasiocampid moths. Using visual fecal inspection with stable isotope analysis provided information on families of moths consumed by an uncommon bat species.