Diets of juvenlle, yearling, and adult big brown bats (Eptesicus fuscus) in southeastern Alberta

We examined dietary characteristics of juvenile, yearling, and adult big brown bats (Eptesicus fuscus) at two maternity colonies in southeastern Alberta, Canada. The diet of E. fuscus included nine orders of insects in 1994 and 1995: Coleoptera, Hemiptera, Lepidoptera, Diptera, Trichoptera, Neuroptera, Hymenoptera, Ephemeroptera, and Homoptera. The diet of adult E. fuscus was dominated by Coleoptera. Juvenile E. fuscus consumed significantly fewer Coleoptera and more Hemiptera than did adults in 1994, but diets did not differ between age classes in 1995. Juveniles included a greater range of and softer items in their diets than did adults. Yearlings (bats that have survived their first winter) and adults did not differ significantly in diet.