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Big Brown Bat

Overview

As with the little brown bat, the big brown bat’s (Eptesicus fuscus) name is highly descriptive. Its fur is uniformly light to dark brown on the upper parts, with slightly paler under parts. The fur is long and silky in appearance, compared to other Ohio bats. The muzzle is not furred. The ears and wing membranes are dark brown to black, and they have relatively large heads with shorter rounded ears compared to the Myotis.

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Description

As with the little brown bat, the big brown bat’s name is highly descriptive. Its fur is uniformly light to dark brown on the upper parts, with slightly paler under parts. The fur is long and silky in appearance, compared to other Ohio bats. The muzzle is not furred. The ears and wing membranes are dark brown to black, and they have relatively large heads with shorter rounded ears compared to the Myotis.

Reproduction

Mating begins in September before bats enter hibernation. Female big brown bat exhibit delayed fertilization, storing sperm until they exit hibernacula in the spring. Gestation lasts 50 to 60 days and pups are born in late May and early June. Big brown bats in the eastern U.S. usually have twins, while big brown bats in the western U.S. have single pups, although it is not known why this occurs. Newborns have hind feet nearly as large as adults, which helps them cling to the walls of the roost.

Habitat & Behavior

During the warm months of the year, big brown bats feed over a variety of habitats, including water, fields, forest openings, and urban and suburban areas. They usually feed one or two hours after sunset and before sunrise. Big brown bats typically eat agricultural pests, like June and cucumber beetles, and stinkbugs; they also eat ants, stoneflies, mayflies, lacewings, and, occasionally, moths. A small colony of 25 bats can eat a pound of insects every night.

Big brown bats use two primary types of habitats: hibernation sites used during the winter (e.g., caves, mines) and roosting sites for rearing young (e.g., buildings and under bridges) during the summer Females form maternity colonies in the spring and summer, generally consisting of 20 to 300 bats. These colonies can often be found in man-made structures like barns and attics. Solitary males roost in tree cavities, buildings, and bridges. Big brown bats are fairly sedentary, and most individuals who are banded are recaptured within 30 miles of their original capture site. From November to March, big browns can be found hibernating alone or in small groups, typically in buildings, but also in mines, and caves. Caves are included in the Cave Protection Act portion of the Ohio Revised Code 1517. This cave protection act ensures that cave life and habitat is conserved, including bats hibernating within them."