The Big Brown Bat: Beautiful Bat Facts

If you live in the United States, it’s likely that the bat you’re most familiar with is the big brown bat (Eptesicus fuscus).

This microbat is 3.9–5.1in long, has a wing span of 11–13in and weighs just 0.49–0.56oz. Its thick fur is a nice uniform medium shade of brown, with the belly being just a shade or two lighter than the back. The short, broad wings are well adapted to lying at a reasonably rate of speed and performing aerial acrobatics as it chases the flying insects it dines on.

At first glance, both male and female big brown bats look identical, but if you see a representative of each gender side by side, you’ll notice the female is titch larger, probably because she’s responsible for raising the pups, which includes carrying them around for a few weeks while the mother hunts.

What makes the big brown bat unique is its range. They can be found throughout the United States and have the distinction of being the bat with the largest range in North America. Big brown bats in different regions have minor physical differences. There are eleven big brown bat subspecies living in the United States.

Sharp teeth and powerful jaws allow the big brown bat to dine on small beetles, which are its favorite prey. The species loves consuming:


·         Cucumber beetles

·         Emerald ash borers

·         Ground beetles

·         Scarab Beetles

·         Snout beetles

·         Stink bugs


When no flying beetles are in the area, big brown bats also like leaf hoppers, a variety of moths, and other mid-sized to small flying insects.

Big brown bats are particularly helpful to vegetable farmers and gardeners. The female routinely consumes her weights worth of insects every single night. A mid-sized colony of just one hundred and fifty bats is large enough to eat enough cucumber beetles to prevent the laying of 33 million eggs.

Maternity colony size varies from as few as twenty bats or as large as three hundred and most of the colony mates share a genetic connection. The males are more solitary ad prefer to roost well away from other males. 

When the weather starts turning chilly, the big brown bats that have been hunting in northern regions fly south in search of a hibernaculum.

Their larger size allows them to stay active long after cool weather forces other bats into hibernation. When they do decide it’s time to hibernate, they prefer to stay in smaller groups and sometimes hibernate by themselves. Preferred hibernaculas are well protected spaces with an internal temperature that range between 32 and 41 degrees Fahrenheit.

Big brown bats have adapted well to human encroachment and don’t appear to mind hunting and roosting in backyards, gardens, and active barns.



Schira, Jess “60 Beautiful Bat Facts.” 2018.







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