Mammals · Chiroptera · Vespertilionidae

Big Brown Bat

Eptesicus fuscus

Least Concern

The species is abundant and widely distributed; it faces no significant short-term risk. See full glossary

The big brown bat is one of the commonest and most urban bats in North America. It breeds in attics, barns and cavities in buildings, and in winter hibernates in caves, mines or even in the buildings themselves. It specialises in beetles, whose hard elytra it crushes with powerful jaws, and for that reason it is regarded as a first-rate agricultural ally. It has withstood the white-nose syndrome fungus far better than other species.

Weight

14 g – 21 g

Size

8 cm – 13 cm

Lifespan

19 years

Diet

Insectivore

Feeds mainly on insects and other invertebrates.

Activity

Nocturnal

Active mainly at night.

Social structure

Colony

Lives in large concentrations, often for breeding reasons.

Sighting difficulty

Easy

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Fun facts

It eats mainly beetles, including several of the main pests of maize and lucerne: a medium-sized colony has been calculated to prevent the hatching of millions of crop-damaging larvae every summer.
It has withstood white-nose syndrome far better than other North American bats, which have lost more than 90% of their numbers: it is one of the few cases that allows any study of why some species resist and others do not.

Life cycle & biology

Skeleton type: Vertebrate - internal bony skeleton (mammal)
Habitat & environment: Attics, barns, tree hollows and caves in woodland, farmland and cities across the Americas
Sexual maturity: 18 months
Gestation / incubation: 35 days
Litter / clutch size: 2

Sources consulted: https://en.wikipedia.org/wiki/Big_brown_bat