Different bat species have different strategies for surviving northern winters. Some migrate to warmer southern regions, some hibernate in caves, mines, or sometimes houses (see Signs That You Might Have Bats in Your Attic). Some species do both. Here in Massachusetts and New Hampshire, we have two different bats that will establish roosts in attics or sheds: the big brown bat and the little brown bat.

The Big Brown Bat Hangs Around in Winter

The big brown bat, in particular, often remains to winter in our region. If you see bats flying about on warm, winter days, they are most likely big brown bats. Little brown bats are more likely to migrate to join large winter colonies in caves or mines as far away as Vermont or New York. Unfortunately, these winter colonies are increasingly infected with a fungal disease, White-nose Syndrome, that is killing bats in huge numbers (see Bats Continue to Die By the Millions From Killer Disease).

In general though, bats in our area hibernate beginning in October or November and remain relatively inactive during winter months. They “wake up” and leave their winter roosts between March and mid-April. Bats then often return to the same nursery sites that they used the year before to have their young. In some cases, that nursery site may be the same location where they spent the winter (your attic?).

Know Local Regulations Before You “Bat-proof”

Bats are beneficial mammals that are protected by the federal government. It is illegal to harass them or remove them from their nesting sites while there may be unweaned young in the colony. By mid-August, though, young bats are generally flying and able to fend for themselves. After mid-August (and before May), bat removal and bat-proofing to seal openings is generally allowed, although the dates may differ slightly from state to state.

Bat-proofing of your home can be done during winter months as long as there are no bats hibernating in your attic (see Batproof Your Home Now to Prevent Summer Roosts.). If bats’ entrances are blocked, they will search for new openings and can end up in living areas. Or, they may eventually die in the attic if they can’t get out to find food.

If you’ve had a problem with bats roosting in your home in the past and want to keep that from happening again, bat exclusion methods (bat-proofing) is the answer. Call Colonial Pest and have our exclusion pros do a thorough inspection for potential bat entrances. We have more than 30 years of experience managing bats in structures and our exclusion work comes with a 7-year warranty.