An evaluation of fecal analysis for determining food habits of insectivorous bats

To evaluate the reliability of fecal analysis in determining food habits of insectivorous bats, individual insects were identified to major taxa by the first author, weighed, enumerated, and fed to 14 female little brown bats (Myotis lucifugus). Fecal pellets were collected from these bats and sent to the second author without informing him of the insects which had been fed to the bats. The second author identified the insect fragments from the feces and determined the percent volume and percent frequency for each taxon. The four most common insect taxa recovered in the feces were the same as those in the diet and occurred in the same order of importance when expressed as percent volume and percent frequency. This blind test is the first to demonstrate that fecal analysis can yield reasonable estimates of food eaten by insectivorous bats, but it also indicates the amount of "error" that one can expect in these kinds of analysis.