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What is a Big Brown Bat?

The Big Brown Bat, a common yet fascinating nocturnal mammal, plays a crucial role in controlling insect populations. With its adept flying abilities and echolocation, it is an essential part of diverse ecosystems.


Known for its resilience and adaptability, the Big Brown Bat is a key species in maintaining ecological balance. Its presence is a natural method for insect control and an indicator of the health of its habitat.


  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Mammalia
  • Order: Chiroptera
  • Family: Vespertilionidae
  • Genus: Eptesicus
  • Species: E. fuscus

Size and Body Description

The Big Brown Bat is relatively large for a bat, with a wingspan of 13 to 16 inches. It has a robust body, broad wings, and a short, rounded muzzle. Its fur is typically dark brown on the back and slightly lighter on the underside.


Wingspan: 13 to 16 inches (33 to 40.6 cm).


Their diet mainly consists of various insects, including beetles, moths, and flies. They are nocturnal feeders, using echolocation to navigate and locate prey in the dark.

Habitat and Range

They are widespread across North America, inhabiting urban, suburban, and rural areas, as well as forests and farmlands.


Big Brown Bats mate in the fall but delay fertilization until the spring. Females usually give birth to one or two pups per year. Being mammals, they do not engage in pollination.

How Long do Big Brown Bats Live

They can live up to 19 years in the wild, though the average lifespan is shorter.

Where Found

Big Brown Bats are found roosting in tree cavities, under bridges, in buildings, and in bat houses. They prefer sheltered spots that provide safety from predators and the elements.


While not endangered, Big Brown Bats face threats from habitat loss, pesticide use, and diseases like white-nose syndrome. Conservation efforts focus on habitat protection and disease research.

The Big Brown Bat, with its nightly insect patrols, is an unsung hero of our ecosystems. Protecting these bats not only preserves a fascinating species but also supports the health of our environment.

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