Bats in the Attic in October: What Should You Do?
If bats are still using your attic in October, the safest response depends on the date, the weather, and whether you are dealing with an attic roost or a bat that has entered living space.
Why October Is Different
Massachusetts homes can host more than one bat species, but the two most closely associated with buildings are little brown bats and big brown bats. By late summer, young bats from maternity colonies are able to fly, which is why fall exclusion becomes possible again after the June–July maternity period.
As autumn progresses, the biology changes. Little brown bats move toward winter hibernation sites, typically caves and mines. Big brown bats are different: they are the Massachusetts bat most likely to spend the winter inside buildings, including cool attics.
In winter, bats survive by lowering their metabolism and living on stored fat. Repeated disturbance can use up those reserves before insects return. Sealing an active roost late in the season can also trap bats inside, where they may die or enter living areas while searching for another way out.
So October is not simply “another month to get rid of bats.” It is the end of a narrow period when a colony can leave under its own power before winter behavior takes over.
What a Proper Exclusion Actually Does
Exclusion is not the same as sealing every crack. Bats can use very small openings, and a house may have several potential entry points. The basic approach is to identify the primary active exit, close other appropriate gaps, and place a one-way device over the active opening so bats can leave but cannot return.
The final opening is sealed only after the exclusion period is complete. This order matters. If the active exit is closed first, bats can be trapped in wall voids or the attic.
Massachusetts landowners can hire a licensed Problem Animal Control (PAC) agent for bat exclusion work. PAC agents are different from municipal animal control officers.
Before and After October 15
| Your situation | Practical response | Why |
|---|---|---|
| It is early October and bats are clearly leaving the attic. | A properly timed exclusion may still be possible. | Young bats are flying, and the permitted fall window is still open. |
| It is only a few days before October 15. | Do not assume there is enough time. Check the weather and the required five-night period before any work begins. | The device must stay in place long enough, and poor weather can extend the process. |
| October 15 has passed and the opening appears active. | Do not begin a new colony exclusion or blindly seal the opening. Document the roost and plan the next appropriate exclusion period. | Big brown bats may remain in buildings to hibernate. |
| You saw no bats on one cold or rainy evening. | Do not treat that single observation as proof the roost is empty. | Bats do not necessarily leave every night, and poor weather suppresses flight. |
Which Massachusetts Resource Applies?
If Contractors Are Already Working on the House
If a roof or siding crew discovers bats in October, stop before sealing the suspected opening. Mark the active route and keep it out of the routine sealing list until someone confirms how the bats are using it.
Other repairs may be able to continue away from the roost, but the active opening should be handled as a wildlife-exclusion point. This is especially important near October 15, when an otherwise simple repair can become a timing problem.
Do not rely on one quiet evening to decide that the opening is unused. A cool, windy, or rainy night can reduce bat activity even when the roost is occupied.
Useful information to give a PAC agent
- The date you first noticed bats or guano.
- Where bats appear to emerge at dusk.
- Whether contractors have already closed nearby gaps.
- Whether any bat has entered bedrooms or other living space.
- Whether anyone or any pet may have had direct contact with a bat.
A clear history can save time because an attic-roost problem and a possible rabies exposure require different decisions.
What to Do After the Fall Window Closes
If bats remain after October 15, you can still identify the active opening, photograph staining or guano, note where sounds are heard, and arrange a professional assessment. The key is to avoid forcing them out once the safe fall exclusion window has closed.
MassWildlife also allows colony exclusion during May, before the summer maternity period. That makes spring the next normal opportunity when conditions are appropriate.
An Attic Roost and a Rabies Exposure Are Different Problems
Bats living in an attic do not automatically mean someone has been exposed to rabies. The concern changes when a bat enters occupied living space and contact cannot be confidently ruled out.
If anyone was bitten or scratched, wash the area thoroughly with soap and water and seek medical advice promptly. For a bat found in a room with a sleeping person, unattended young child, mentally incapacitated person, or pet, contact the local board of health. The Massachusetts Department of Public Health Division of Epidemiology and Immunization can also be reached at 617-983-6800.
For a bat that has entered a bedroom or other living space, use our bat-in-house guide. That situation can involve rabies-exposure questions and should be handled differently from bats confined to an attic.
Common Questions
Can I seal a bat opening in early October?
Only after a proper exclusion has allowed the bats to leave. Massachusetts permits fall exclusion from August 1 through October 15; the active opening should not simply be sealed while bats may still be inside.
What if October 15 is only a few days away?
Do not race the calendar. The one-way device needs at least five nights and suitable weather. If that process cannot be completed properly, shift to assessment and plan the work for a permitted period.
Can one quiet evening prove the attic is empty?
No. Not every bat exits every night, and cold, wind, or heavy rain can suppress flight. One observation is not enough to justify sealing a suspected active opening.
Why not exclude bats in winter?
Big brown bats commonly hibernate in Massachusetts buildings. Winter disturbance can consume critical fat reserves, and sealing an active roost can trap bats inside.
Guidance basis: MassWildlife's Bats in the Home and Massachusetts Homeowner's Guide to Bats, plus Massachusetts Department of Public Health rabies guidance. Reviewed August 2026.