An online resource based on the award-winning nature guide –

Big Brown Bats Entering Hibernation

11-7-14  big brown bat IMG_7011Big Brown Bats, one of the most widespread mammals of North America, are one of the last species of bat to be seen flying in the fall. A relatively hardy species, the Big Brown Bat can tolerate conditions that other bats can’t. However, once cold weather arrives in the late fall and the nighttime temperatures dip down into the 30’s, they go into hibernation.

Both the Big Brown Bat and the endangered Little Brown Bat are considered “house bats,” because they are the most common bats found in houses in both summer and winter. During October, November and December, Big Brown Bats seek out caves, buildings and mines in which to hibernate. Some may migrate short distances to find an appropriate location for hibernating, but many find hibernacula close to their summer residence. Individuals often become active for brief periods during the winter months, sometimes even changing hibernation sites. Big Brown Bats can live up to 18-20 years in the wild but, unfortunately, most Big Brown Bats die during their first winter because they did not store enough fat to survive through their entire hibernation period.

Naturally Curious is supported by donations. If you choose to contribute, you may go to and click on the yellow “donate” button.

7 responses

  1. Kathie Fiveash

    Are big brown bats as vulnerable to white nose syndrome as little brown bats? Are their numbers plummeting?

    November 3, 2014 at 11:57 am

    • No, Kathie, big brown bats seem to have come through relatively unscathed, comparatively speaking…

      November 3, 2014 at 12:19 pm

  2. Mary,

    I love your emails!

    And, want to purchase several of your 2015 calendars. What’s the best way to do that?



    Alex Risley Schroeder

    Principal, Finding Earth Works


    Giving adult learners a stake in the green economy.

    Finding Earth Works connects adult literacy and English language students and programs to information and training about green jobs.

    November 3, 2014 at 2:13 pm

  3. I love bats and wish we had more. The most I saw at one time this summer was three. I want a colony!

    November 3, 2014 at 9:27 pm

    • Me, too. (I could write that after all of your comments, Eliza!)

      November 3, 2014 at 9:51 pm

  4. kathy mcgreavy

    Hi Mary, Are the big brown bats being affected by the white nose disease as are the small brown bats?

    November 9, 2014 at 12:12 pm

    • No, they are not, at least not in Vermont, and I don’t believe elsewhere. They are relatively unscathed by it.

      November 9, 2014 at 5:24 pm

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s