Awaiting expert review. This page covers safety or regulatory rules that change over time. It is kept out of search results until a qualified reviewer has checked it; the sources below are dated so you can verify each point.
Quick answer
Bat exclusion is the humane removal of bats from a building by sealing every secondary gap, fitting one-way exit devices over the openings bats use so they can leave but not return, and then sealing those openings once all bats are gone.
It is done outside the summer nursery season so flightless pups are not trapped inside. No pesticides are registered to kill bats in buildings, so exclusion is the standard method.
Quick facts
The key facts about Bat Exclusion, with sources:
Key takeaways
- Bat exclusion lets bats leave on their own through a one-way door, then closes the door for good.
- Doing it in early summer traps flightless pups inside, which kills them, can break state law and leaves odor problems.
- Bats can squeeze through gaps about 1/4 inch wide, so every crack must be found and sealed.
- Any bat that may have touched a person, or was found in a room with a sleeping person or child, is a health department matter first.
- Never use poison, glue boards or repellents; none are registered to kill bats, and New Jersey forbids lethal methods.
How bat exclusion removes bats without harm
When bats roost in attics, walls, soffits or behind shutters, bat exclusion gets them out without killing them: a worker finds the holes the bats use, seals all the others, and puts a one-way door over the main exit.
Bats fly out at dusk to feed and cannot get back in, and after a set time the last openings are sealed 12.
Exclusion is the standard for practical and legal reasons: UC IPM says no pesticides or chemical repellents are registered in California to control bats, and ultrasonic devices have proven ineffective 2.
Many states protect native bats, and New Jersey protects all native nongame wildlife and says no lethal means should be used on any bat 1.
Bats are worth keeping alive, since almost all of California’s 25 bat species eat insects 2.
White-nose syndrome, a fungal disease of hibernating bats, had killed more than six million bats in North America by 2016, about a decade after it was first seen in New York in the winter of 2006–2007 5. Exclusion keeps them out of your home while leaving them alive.
Exclusion is not removal by hand
In a proper exclusion, no one catches or handles the bats. They leave by themselves through a one-way device. A bat that is easy to catch is likely sick, and UC IPM says only an expert should handle one 2.
How bat exclusion works, step by step
This sequence follows New Jersey’s nuisance wildlife guidelines for bats and UC IPM 12. It describes professional work.
- Inspect and watch. The contractor checks the outside for gaps and stains, then watches bats leave at dusk to find the main exits 1.
- Seal the minor gaps. All secondary cracks and holes are sealed while the main exits stay open 1.
- Fit one-way devices. Netting or tubes go over each main exit so bats can leave but not get back in 12.
- Wait. New Jersey requires at least one week, including at least three nights in a row above 50°F with wind under 10 mph and no steady rain 1.
- Confirm they are gone. The exits are watched at dusk on the last night to be sure no bats remain 1.
- Seal for good. The devices come off and the exits are closed with lasting materials 1.
- Offer another home. A bat house put up before the work gives the colony somewhere to go instead of a neighbor’s attic 1.
- SurveyFind exits at dusk
- Seal side gapsLeave main exits open
- One-way devicesBats leave, cannot return
- Wait 7+ daysWith warm, calm nights
- Final checkWatch the last emergence
- Seal exitsPermanent repair
Waiting period and weather terms are New Jersey Division of Fish and Wildlife guidance; UC IPM also gives 7 days. Source: [1] [2]
Kinds of bat work and when each applies
| Job | What it is | When it fits |
|---|---|---|
| Full exclusion | Seal side gaps, one-way devices, final seal 1 | A colony roosting in an attic or wall, outside the nursery season 1 |
| Bat-proofing only | Seal gaps when no bats are present 3 | After bats leave in fall or winter 3 |
| Winter exclusion without devices | Allowed in NJ only if bats are shown to be absent, e.g. 3 weeks of acoustic monitoring 1 | Oct 16–Mar 31 in New Jersey 1 |
| Blocking living-space entries | Close gaps into rooms people use 1 | Any time, if it does not trap bats or shut them out of the roost in a restricted period 1 |
| Single bat indoors | Health department or animal control decides on testing 3 | A bat inside the living area |
Example: planning an exclusion around New Jersey’s calendar
An illustration using New Jersey’s published windows 1. Other states set different dates; this is not advice for your state.
| Bats found | NJ rule | What happens next |
|---|---|---|
| Early April | Exclusion allowed April 1–30 1 | Book now; devices need a week of warm, calm nights |
| Mid-June | No exclusion May 1–July 31: nursery colonies active 1 | Wait until August 1; block only entries into living space |
| Late August | Exclusion allowed Aug 1–Oct 15 1 | Good window; pups can fly by then |
| December | Oct 16–Mar 31 restricted to protect hibernating bats 1 | Work only if acoustic monitoring shows bats are absent |
The pattern: in New Jersey, a homeowner who finds bats in June waits about six weeks. Sealing early would trap pups. New Jersey says that can be an illegal take, push bats into new entry points, and cause odor from dead young 1.
Where bat exclusion shows up on paperwork
A wildlife or pest company’s proposal should list the entry points found, the materials used to seal them, the number of one-way devices, how long they stay up, and the date of the final seal. New Jersey suggests contractors consider certification as “Bat Standards Compliant” through the National Wildlife Control Operators Association 1.
A home inspection report may note “evidence of bats” from droppings or staining near gaps. UC IPM notes bat droppings crumble easily and show shiny insect bits, unlike mouse droppings 2. For rodent signs, see our rodent droppings page.
A health department letter may follow if a bat had contact with a person. Keep it with your records. For general wildlife work, see our rodent and wildlife control service.
Signs bats are using your building
- Bats flying out of a roof edge, soffit, vent or chimney at dusk.
- Dark stains from body oils and urine around a gap 2.
- Droppings that crumble into shiny insect bits, never white or chalky like bird droppings 2.
- Squeaking or scratching in the walls or attic, especially at dusk and dawn.
- A bat in the living area, which may mean a gap into the house.
- Bed-bug-like insects near the roost; bat bugs need a bat host to breed 2, and our bed bug guide explains how to tell them apart.
Rabies: do not touch a bat
Bats are the most reported rabid animals in the U.S., and most people in the U.S. who die of rabies were exposed to a bat 3. Bat bites can be tiny.
If anyone may have been bitten or scratched, wash the area with soap and water and get medical help right away. Call your health department or animal control before letting any bat go 3. Do not try to catch it yourself.
Why exclusion is the standard, and its trade-offs
Strengths
Where bat exclusion falls short
Hibernating bats are hard to detect. New Jersey notes they are largely inactive, make few droppings and do not roost in the open in winter, so a visual check cannot rule them out 1. That is why New Jersey asks for at least three weeks of acoustic monitoring before winter work 1.
Older buildings are hard to seal because tile roofs, loose siding and chimneys offer many openings. UC IPM lists chimney caps, mesh and bird-stop strips among the fixes 2.
Repellents are no substitute for sealing, because UC IPM reports that every ultrasonic device tested proved ineffective 2.
What drives the cost of bat exclusion
Bat jobs vary too much by roof and season for us to print a price without many dated local quotes. What we can describe is what moves the price.
The number of gaps and how high they sit matter most, so a single-story ranch with one exit is quicker than a three-story home with tile roof and many seams. The number of one-way devices, the return visits to check and remove them, and lift or ladder work all add time.
Droppings clean-up and attic insulation replacement are often separate lines. Ask whether the price includes a warranty on the seal work and for how long. Our pest control cost guide explains how to compare quotes line by line.
How to get a bat exclusion done right
- Check for contact first. If a bat was in a room with a sleeping person, a child or anyone who may have been bitten, call your health department before anything else 3.
- Find the date window. Ask your state wildlife agency when exclusion is allowed, because New Jersey and California give different periods 12.
- Hire the right contractor. Many states license nuisance wildlife operators separately from pest control. Check with our license lookup and the licensing guide.
- Get a written scope. Entry points, materials, device count, timing and warranty.
- Consider a bat house. Install it before the work so bats can find it 1.
- Plan clean-up. Droppings removal is a separate task with its own health precautions 2.
Droppings and dust
Histoplasmosis is a lung infection from breathing fungal spores; the fungus spreads through bird and bat droppings mixed into soil and is mainly found in central and eastern states 4. UC IPM recommends a respirator that filters particles down to 2 micrometers when cleaning droppings 2. Leave large clean-ups to professionals.
Keeping bats out after the job
- Walk around the house each fall and look for new gaps larger than about 1/4 inch 3.
- Keep chimney caps and vent screens in good repair 2.
- Make sure attic doors close tightly and holes for wires and pipes stay filled 3.
- Watch the roofline at dusk in late spring for bats returning to old spots.
- Keep the bat house up; it may sit empty for a year or more before bats use it 2.
Sealing work for bats overlaps with general pest entry point repair; the pest risk checklist covers the rest of the house.
When to call, and whom
Call your local health department or animal control right away if a bat was found in a room with a sleeping person, a child or someone who cannot say whether they were bitten, or if anyone touched a bat 3. Medical advice comes first and exclusion can wait.
Call a licensed wildlife control operator when bats are roosting in the building, and avoid anyone who offers poison, glue boards or summer sealing.
Laws and rules that govern bat exclusion
New Jersey (NJ Division of Fish and Wildlife). The Endangered and Nongame Species Conservation Act (N.J.S.A. 23:2A-1 to 13) makes it illegal to take native nongame wildlife, including bats.
The Division’s Nuisance Wildlife Control Guidelines for Bats (updated 13 February 2019) allow exclusion April 1–30 and August 1–October 15, bar it May 1–July 31, and restrict it October 16–March 31.
Exceptions need a health department finding of imminent threat, made with the Division 1.
California (UC IPM guidance). UC IPM advises against exclusion from May through September, when flightless young may be present, and notes no pesticides are registered in California to control bats 2.
Federal. Some bat species are federally listed; the CDC tells homeowners to check local rules because some bats are endangered and may need special care 3. Pesticides are regulated by the EPA under FIFRA, and none may be used on bats unless the label allows it.
Other states. Dates and permit rules vary. Ask your state wildlife agency before booking work.
Bat exclusion vs other wildlife approaches
| Approach | For | Key difference |
|---|---|---|
| Bat exclusion | Bat colonies in buildings | Timed to nursery and hibernation rules; no handling 1 |
| Wildlife exclusion | Raccoons, squirrels and other animals | Different species rules and denning seasons |
| Rodent exclusion | Mice and rats | Smaller gaps; trapping is routine |
| Lethal control | Not used for bats | NJ says no lethal means for any bat; no pesticides registered in CA 12 |
Bat exclusion myths
- Myth Most bats have rabies.
- Reality No more than 0.5% of randomly tested bats were rabid 2, but any contact still needs medical advice 3.
- Myth Sealing the holes in June is fine.
- Reality It traps pups that cannot fly; New Jersey bars exclusion May 1–July 31 1.
- Myth A sonic repeller will drive them out.
- Reality UC IPM says tested ultrasonic devices proved ineffective 2.
- Myth Mothballs or a spray will work.
- Reality No pesticides or chemical repellents are registered in California for bats 2.
- Myth A bat flying in the house is attacking.
- Reality NJ notes bats in flight are very likely healthy; the concern is contact, which the health department assesses 1.
Why the calendar depends on your state
Bat exclusion is governed by state wildlife law, and the dates differ. New Jersey bars exclusion May 1–July 31 and restricts it October 16–March 31 1.
UC IPM advises Californians to avoid May through September 2. Histoplasma, the fungus linked to droppings, is mainly found in central and eastern states 4. Check your state wildlife agency’s current rule before scheduling.
What to do now
Start with contact: if there is any chance a bat touched someone, call the health department today. Then check the calendar. If you are inside your state’s nursery window, block only gaps into living space and book the exclusion for the next open window. If you are outside it, book a licensed exclusion now.
Ask for a written scope with every entry point, device count, final seal date and warranty.
Decision guide
A possible bite or a bat in a bedroom means the health department first. A colony in the attic in summer means waiting for the legal window. A colony in the attic during an open window means a licensed exclusion now. Never poison, glue or seal with bats inside.
Questions about Bat Exclusion
When is the best time for bat exclusion?
Fall or winter after bats leave is best, along with any spring and late-summer windows your state allows.
The CDC says most bats migrate in fall or winter, which makes those the best times to bat-proof, and warns against trapping young bats from May through August.
New Jersey allows exclusion April 1–30 and August 1–October 15. Avoid early summer, when pups that cannot fly are inside.
Is it illegal to kill bats?
In many states, yes. New Jersey protects all native nongame wildlife under its Endangered and Nongame Species Conservation Act and says no lethal means should be used on any bat. Some bat species are also federally listed. UC IPM notes no pesticides are registered in California to control bats. Exclusion is the legal, standard method.
What should I do if I wake up with a bat in my room?
Call your local health department or animal control right away and do not release the bat until you have spoken to them.
Bat bites can be so small you do not notice them, and the CDC says most U.S. rabies deaths come from bat exposures.
The health department will decide whether the bat should be tested and whether you need treatment.
How small a hole can a bat get through?
Bats can squeeze through openings about 1/4 inch wide, according to the CDC and UC IPM. The CDC advises caulking openings larger than a dime.
UC IPM says to seal holes larger than 1/2 inch and cracks 1/4 by 1 1/2 inches or bigger. That is why exclusion work checks every seam on the roofline and walls.
How long does bat exclusion take?
The one-way devices usually stay up at least a week. New Jersey requires a minimum of one week, including at least three nights in a row above 50°F with low wind and no steady rain, and UC IPM gives 7 days.
Add time for the first inspection, sealing side gaps and a final dusk check before the exits are closed.
Do bats in the attic carry rabies?
Very few do. UC IPM reports that no more than 0.5% of randomly tested bats have been rabid. But bats are the most commonly reported rabid animals in the U.S., so any bite, scratch or unclear contact needs medical advice. Never touch a bat with bare hands.
Can I seal the holes myself once bats leave at night?
Doing it yourself is not safe. Some bats stay behind each night, and in early summer pups that cannot fly remain inside. Sealing then traps them, which New Jersey says can be an illegal take and causes odor problems. One-way devices and a waiting period are what make an exclusion humane and legal.
Are bat droppings dangerous?
Old droppings can be a health risk. Histoplasmosis is a lung infection from breathing fungal spores, and the fungus spreads through bird and bat droppings mixed into soil, mainly in central and eastern states, per the CDC.
UC IPM recommends a respirator rated for particles down to 2 micrometers when cleaning droppings. Large clean-ups are best left to professionals.
Will a bat house keep bats out of my attic?
A bat house can give an evicted colony a nearby place to go, so it is less likely to move into a neighbor’s home, as New Jersey suggests. It does not replace sealing.
UC IPM notes a bat house may sit empty for a year or more, and works best mounted at least 10 feet high and installed before March.
Sources
- New Jersey Division of Fish and Wildlife, Nuisance Wildlife Control Guidelines for Bats (updated 2019-02-13), retrieved .
- UC Statewide IPM Program, Pest Notes: Bats (Publication 74150), retrieved .
- U.S. CDC, Rabies and Bats, retrieved .
- U.S. CDC, About Histoplasmosis, retrieved .
- U.S. Fish and Wildlife Service, Bat with White-nose Syndrome Confirmed in Washington State (press release, 2016-03-31), retrieved .
Expert review
Written by the HyrePest Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Exclusion method, waiting period and New Jersey date windows follow the NJ Division of Fish and Wildlife guidelines (updated 2019-02-13). Opening sizes, California timing, rabies rate, pesticide status and droppings advice follow UC IPM Pest Notes 74150.
Rabies and contact guidance follow the CDC. Histoplasmosis facts follow the CDC. White-nose syndrome facts follow USFWS. Held for G-REV: a state bat biologist or wildlife agency must confirm the exclusion windows. No prices given.
Suggest a correction. We fix errors and say what changed.