Gray Bat - Diet

Diet

Gray bats consume a variety of insects including Coleoptera (beetles), Diptera (flies), Ephemeroptera (mayflies, of which Gray Bats consume at least six species), Lepidoptera (moths), Neuroptera (net-winged insects), Trichoptera (caddis flies), and Plecoptera (stoneflies). Juveniles have a tendency to forage more in woodlands and eat more beetles than adults, perhaps they provide a greater energy reward per unit of capture effort. For example, beetles provide 1900-2800 calories/g wet weight versus 800-1400 calories/g wet weight for mayflies. M. grisescens juveniles also eat a less diverse diet than adults, possibly because juveniles are more dependent on high concentrations of prey or swarming prey. Gray bats are believed to be part opportunists, and part selective eaters. (Outside of captivity, gray bats are limited by the sporadic emergences of potential prey. When prey emerges, there is only an abundance of a few taxa at any given time. The available taxa change based on the time of night, the month, and the time during the activity season.) In their natural habitats, gray bats appear to attack any moving target that is of appropriate size, consistent with optimal foraging theory that predicts palatable insects of an appropriate size should be eaten when encountered. In captivity, under controlled laboratory conditions, however, insectivorous bats used echolocation to discriminate heavily among potential prey based on shape and texture of a target. This lack of discrimination may be because of the rapid flight of bats and the short range at which prey can be detected using echolocation, allowing bats only a fraction of a second after detection to capture prey. However, gray bats are believed to discriminate somewhat between insects when foraging in their natural habitat, consuming higher numbers of Lepidoptera, Coleoptera, Diptera, and in some populations Trichoptera, than their proportional prevalence would have otherwise indicated without selective foraging. Because of this tendency to select prey while being largely opportunistic, gray bats have been dubbed ‘selective opportunists’. Scientists believe that food moves quickly through the digestive tract of M. grisescens, with feces being purged from the body within 1–2 hours prior to ingestion.