May 30, 2007

Bats, Bat Removal, Bat Behavior

For the last few years the building I live in has been home to a large colony of bats. Hopefully readers will find my experiences of removing the bats and my observations of bat behavior helpful and educational. For brevity I have omitted many events and details.

I live in a multifamily condominium in the northwestern part of South Carolina. My unit consists of two floors at one end of the building. For two summers I heard noises in my outer wall. I assumed the noises were made by birds, since birds getting into the attic has been a recurring problem here. One evening in late August 2006, neighbors noticed bats emerging from under the vinyl flashing at the roof's peak. I went out and watched. There were hundreds of bats. Neighbors contacted the company that manages the condominiums. The management company hired a local pest-control company that wanted to hang bags of BAT-A-Way (i.e. naphthalene, moth balls) in the attic.

I am sensitive to moth balls. Whenever I am exposed to moth balls I get a bad headache, my eyes burn, and my stomach feels queasy. I would not allow the pest-control company to put naphthalene in the attic. I researched naphthalene and discovered it not only causes headaches and nausea, but it can also damage the liver and kidneys, and may cause cataracts. Here are two material safety data sheets on Naphthalene: MSDS 1, MSDS 2. Many Internet sites sell naphthalene bat repellent, however they list the states to which they can not legally ship the product, which seems to confirm the hazardous nature of the product. I found several sites that say bat repellents do not work. One such site, Bat Repellent - Does It Work? says the following, "There is no such thing as an effective bat repellent. Period.... The internet is full of bat deterrent products, but none of them work.... I've seen people dump OVER 50 POUNDS of mothballs in an attic where bats are living, and they don't care in the slightest. They keep using the area."

There is an effective and humane way to get rid of bats (sometimes called "bat exclusion"). The beauty and cleverness of getting rid of bats through exclusion is that the bats leave on their own. There's no attempt at bat removal. You make it so bats can't get back in after they have left. The next time the bats go out to feed on insects they can't get back in.

Exclusions should not be attempted if there are baby bats in the building. Like all baby mammals, baby bats are nursed by their mothers until they can fly to hunt for insects on their own. In this part of the United States the nursery period seems to be late May to late August. You should wait until all the babies can fly before excluding the bats.

Bat Exclusion Steps
1. Discover all the openings bats can use to get in and out of the building.
2. Seal all the openings except for the most-used opening.
3. Make it so bats can exit the most-used opening, but can't get back in.
4. Wait until all the bats have left.
5. Permanently seal the last opening.

Hundreds of bats left a couple of days after we discovered them. In the following days only 20-30 bats left to feed each night. A man came and hung sheets of black plastic attached to the flashing with duct tape. The plan was that the bats would drop from behind the flashing and not be able to find their way back in. It didn't work. More often than not the plastic was standing out from the building due to the breeze, then it blew onto the roof so that it wasn't hanging at all, then the duct tape came loose and the plastic fell to the ground. There continued to be 20-30 bats every night. Hundreds of bats returned during the last week of September. I watched and counted for a half hour before dark one night and counted 1,409 bats exit. A neighbor whose night vision is better than mine said at least as many bats emerged after dark as before dark. That meant our colony had close to 3,000 bats. The next night I took pictures with my digital camera as the bats flew out.

Since the management company wasn't getting rid of the bats, and since I was the one who forbade them to use naphthalene, I decided to take action. On September 29 I went to Lowe's and Home Depot in search of ¼-inch polypropylene screen. Neither store had it, nor anything close. Both stores had window screen and bird netting (to protect fruit trees), but no screen size in between. The holes in the bird netting were too large (at least ½-inch), plus the netting was so light and flimsy I was afraid it would work like a fish net and entangle the bats. I settled for the cheapest nylon window screen. I designed and partially built my screen before going onto the roof. I straightened out metal clothes hangers and threaded them along the bottom of the screen for weight. I covered the hanger ends with duct tape to prevent slippage. During the nightly watches neighbors had seen bats exiting from the base of a chimney. I inspected the base of the chimney and discovered a metal plate had popped up leaving a large opening into the attic through which I could smell bats. I got nails and hammered the plate down securely. I installed my screen. Duct tape does not adhere to screen well. So I put duct tape along the upper screen edges and stapled the duct tape to the screen. Duct tape sticks to vinyl flashing well and it sticks to itself. I used duct tape to hold the screen to the flashing. (I stapled the top edge of the screen to narrow wooden boards which I laid along the edge of the roof and duct-taped to the shingles. I didn't want to make holes in the shingles with nails. Duct tape doesn't hold well through wind and rain. Later I used one screw in the center of each wooden board affixing it to the flashing.) The screen concept was good, but I hadn't made it wide enough. The next day I added an extension and wedged duct tape into the crevice under the flashing on both sides of the screen.

The screen worked! The nightly bat count went from over 1,400 to 2 bats in one day. The two bats that continued to come and go were seen landing on the brick wall below the screen and crawling up the wall behind the screen to the opening. I don't know if those two bats were a different species, smarter, or just the most persistent. A few days later those two bats appeared to be gone too. We decided to wait for cold weather, remove the screen, and seal the crevice.

On January 17, 2007 men came, removed my screen, and hammered the flashing. I alerted management that the crevice still looked too wide. Men came and hammered the flashing again. The crevice still looked too wide. During February a few bats returned and on March 3 I counted 27 bats come out from under the flashing. I had gotten rid of the bats only to have the management company remove my screen, not seal the crevice, and let the bats back in! If 27 bats could get in, so could 3,000.

Men came and installed a new exclusion screen, but they didn't make it hang straight, they didn't weight it, and they didn't seal the crevices on either side of the screen. More bats came until there were hundreds again. On March 9 a man came and removed the flashing, in order to install new flashing and seal the attic. Neighbors saw what he was doing, knew there were hundreds of bats in the attic, and made the man leave without sealing the opening. With the vinyl flashing gone I could see the opening the bats had been using. It was perhaps eight inches by one inch. The bats had been coming out of that hole and crawling behind the flashing to drop out from behind the flashing.

Finally the management company did what should have been done the previous summer. They hired a company that knows how to get rid of bats, Critter Control. The two guys that came from Critter Control were great. They examined the roof for other possible openings and asked me a lot of questions. They understood the problem, knew exactly what to do, and had the right tools. They sealed the narrow crevices between the wood and the brick with a polymer foam resin. They left one hole at the peak to which they attached an exit pipe. They said the bats would exit through the pipe but not be able to find their way back in through the pipe.

That night some bats discovered they could squeeze out from under a roof shingle at the corner. After four days all the bats had found their way out, either through the pipe or the corner. The following week the Critter Control guys sealed the corner under the shingle and decided to leave the pipe up a few more days in case bats had been getting back in through the corner. All the bats are gone now. The Critter Control guys came and removed the exit pipe on April 10. On May 8 new flashing was installed along the roof's edge.

Bat Behavior

I watched the bats almost every night for several months. I made several interesting observations. I do not know if these observations were true only for the spiecies I watched, or if other species of bats act the same way.

The colony contained at least two distinct groups, possibly different species. Each group had its own preferred exit time. One group exited 30-40 minutes before the second group. The second group exited for about ten minutes right before dark. In February I noticed the bats began their exit each day about three minutes later than the previous day.

Bats do not feed every night. During an exclusion the exclusion device should be left up for several days to make sure all the bats have exited.

Bats come and go all night. During the nights when there were only two bats I noticed they would feed for two to three hours, return, wait a few hours, and leave again.

Bats do not only feed at night. During February when the nights were cold bats left to feed in broad daylight and returned around sundown before the temperature dropped.

Bats often urinate immediately after they exit. I was hit several times during my first few bat watches and wore a wide-brimmed hat thereafter.

Bats can fly and feed in the rain. Some days when it was drizzling I assumed the bats wouldn't feed. I assumed the rain would interfere with their echolocation navigation. I assumed the rain would down the flying insects on which bats feed. My assumptions were wrong. I saw bats leaving to feed several times during gentle rains.

I read on at least one web site that bats don't fly when the air temperature is below 45 degrees Fahrenheit. That's not true. I saw bats leaving and returning several times when the temperature was about 40 degrees Fahrenheit.

Bats are programmed to enter a structure exactly where they exited. This behavior became apparent to me as I fine-tuned my exclusion screen. When I put the screen up the bats didn't want to exit through the opening behind the screen because they couldn't get back in that way. Even though there was a wide opening for them to drop through behind the screen they crawled behind the flashing until they found a spot where they could drop out from behind the flashing. Later, they returned to the spot where they had dropped out of the flashing rather than to the opening behind the screen. When Critter Control installed the exit pipe the bats refused to exit through the pipe for hours. Instead, the bats searched for another way out. That's when they discovered they could push up a corner shingle to get out.

With the occasional rare exception bats land directly on the opening from which they exited. If the opening is difficult to get into, a bat may make many landing attempts before successfully entering the hole. A bat will try to land on the hole, fail, fly another loop, and repeat the landing attempt. In general a bat will not land near a hole and crawl to the hole.


Anonymous David said...

That was a very interesting experience to read.. I stumbled upon this while searching google for ways to evict some bats from my own attic.

Thanks for sharing.

August 11, 2008 at 1:07 PM  
Blogger Jon Maloney said...

Thanks for your comment, David. I put a lot of effort into that post over a year ago. I'm glad at least someone read and appreciated it. (grin)

During the summers when the attic was filled with bats we had no mosquito problem here. Now that the bats are gone the mosquitoes are back. I like bats and wished they had found another place to roost nearby. I just didn't want them in my attic and walls.

Good luck with your bat problem.


August 11, 2008 at 1:36 PM  
Anonymous Scott said...

Thanks for posting about your experience and solution Jon. I am a Nuisance Wildlife Control Operator, and one of the services that I provide is humane bat exclusion. I love bats...just not in (our) homes! I learned several things from your blog that I hadn't known previously, and it will help to improve my skills for future clients (both bats and people!).


August 12, 2008 at 9:59 AM  
Blogger Jon Maloney said...

I'm glad you found my bat post helpful, Scott. Thanks for commenting.

August 12, 2008 at 10:33 AM  
Anonymous Anonymous said...

great stuff thanks for cutting thru the crap. is the exit downspout pipe and was there any thing else inside? thanks barry

August 19, 2008 at 12:24 PM  
Blogger Jon Maloney said...

Hi Barry,

I didn't go up on the roof after Critter Control installed the pipe, so I never saw it up close. I don't think there was anything inside the pipe. From the ground it looked like they had made it out of standard downspout segments. It looked like they covered the gap under the peak with heavy metal screen. They cut an opening in the screen exactly big enough for the pipe and somehow attached the pipe. I don't know how. I think the pipe's end would need to be flush with the screen, or almost flush. Otherwise bats crawling along the screen looking for a way out wouldn't find the opening. Bats can crawl through very small crevices, so everything built to manage them must be tight.

Thanks for your comment.


August 19, 2008 at 12:49 PM  
Anonymous Becki said...

I have been dealing with bats in my attic for over a year now and can't afford for the professionals to come out and help (they charge over $850). I love the details you put into your blog and the pictures!! I didn't realize that they exit at different times....I'll have to start watching longer to evaluate our situation better (I only keep seeing 1-2 but I have had 4 make it into the living area of our home) My problem is my house is a 2 story with a full attic, so its pretty tall (basically a 3 story) and I can't get to the roof! Thanks for taking the time to educate me.

August 30, 2008 at 8:59 AM  
Blogger Jon Maloney said...

Hi Becki,

The building I live in is a two-story brick building with six living units. Although it has a large common attic the bats were roosting in the north wall of the building. When we had over a thousand bats coming out every night, a guy with a flashlight searched the attic during the daytime and found no bats. That's not pertinent to your comment, but your comment made me think of it and I thought some people might like the additional information.

If you have had four bats in the living space of your home, there's probably a way into your home from the attic. That presents a problem because if you attempt to use a no-reentry technique to get rid of the bats, they will seek and find an alternate exit. As we found when Critter Control put the exclusion pipe at the peak, the bats didn't want to exit through the pipe and searched for another way out. They found they could exit under a shingle at a corner. In your case it sounds like the bats would find their way into your living space. You will need to find and seal any openings between the attic and your home's living space.

If you want to find the ways bats are entering and exiting your attic you need to hold nightly bat watches for several days, with people positioned to watch your house from every direction until long after dark.

Thanks for your comment.

Good luck!


August 30, 2008 at 9:35 AM  
Anonymous Karen said...

Has anyone had to deal with quano removal? I understand it can be quite expensive.

September 6, 2008 at 4:46 PM  
Blogger Erik Rivas said...

Jon: Thanks for taking the time to post your experience with bats. It certainly was entertaining as was educating. I bought a beach cottage in El Salvador and there is bat activity around the property. I now know why. They are atracted to the mosquitoes, especially in the rainy season when they proliferate. Now they won't bother me so much since they will control the peskier mosquitoes.


March 20, 2009 at 9:54 PM  
Blogger quiel said...

Thank you so much for posting your experience! We bought our house 3 years ago and have recently come to find out we have quite the colony living in our attic. We've been up in the attic about a year ago to see if it was worthy of making into a useable room. When I shined the flashlight at the walls I didn't see anything hanging on the walls but we did notice animal droppings throughout the insulation that was laying on the floor of the attic (insulation is about 1 1/2 to 2 feet thick throughout the room). We can hear the bats in the attic from outside the house and last night witnessed approximatly 100 of them fly out from under our shingles and out of our chimney. We've only found 2 inside the house itelf (in living room and kitchen sink).

Knowing they're living in our attic I now don't think I want to turn our attic into a useable room anymore. Even if we get a bat exterminator to remove them. Yuck!

July 24, 2009 at 11:07 AM  
Anonymous Miriam Anderson said...

We are living in Zimbabwe and have had five bats come into our living quarters, looking up into the canister lights tonight I could see straight up to the roof! Guess what was hanging there? More bats, ugh. We dealt with hundred or so bats in an old house in Dupont here in Africa! Ick. Just wish they would camp out somewhere else. Im giving this article to the people who take care of the maintenance of the house... maybe it will help. Hope so. Thanks for the post.

December 12, 2009 at 3:07 PM  
Blogger Jon Maloney said...

I feel for you, Miriam. I hope my post helps your maintenance folks. I loved having lots of bats around for the way they eliminated mosquitoes in the area, but bats sure are difficult to get out of your house. It would be great if neighborhoods built big bat houses that the bats found more attractive than people houses. Then both the bats and the people would be happy.

December 13, 2009 at 10:34 AM  
Anonymous Anonymous said...

Temporarily affix flood lights to the post that is in support of the new bat house and in so doing attract flying insects and their natural predator -- the bat. Depending upon geography and the type of bats you have in the area - set up the lighted bat house just prior to the mating season. Once the bats have moved into their new quarters -- remove the lighting. Prior to spotlighting the new bat house -- be sure that your own house cannot be infiltrated by bats!

May 20, 2010 at 3:38 PM  
Blogger Jon Maloney said...

Thanks for posting the tip. Many years ago I gave my parents a bat house, which they affixed to their house near the attic vents in hopes of luring the bats out of the vents. The bats preferred the vents and never used the bat house.

May 20, 2010 at 3:44 PM  
Anonymous Anonymous said...

How can you tell if you have bats? Recently I hear noise in the attic that almost sounds like birds on the roof. It happens right before dawn. Interestingly, I have never been bitten by a mosquito in the 6 years I've lived in this house...

June 6, 2010 at 11:29 AM  
Blogger Jon Maloney said...

You might hear noises from your attic and roof from birds, squirrels, rats, bats, or other animals depending on where you live. The best way to know if you have bats is to see them. You can watch around your house's roof for about a half hour at dusk to see if any bats come out to feed.


June 6, 2010 at 11:46 AM  
Anonymous Anonymous said...

this was a fasinating read, I have just counted 27 bats coming out of a tiny gap between top of house and eves, and can hear more, hopefully not as many as you had, I would,nt mind if they were not so noisy but as they are nesting in the cavity of my bedroom they keep me awake, I,m in the midlands of Ireland if anyone knows a company to get rid of them for me? Vivienne

July 2, 2010 at 5:35 PM  
Blogger Jon Maloney said...


I performed some Internet searches and learned that bats are protected in Ireland. It's illegal to harm them or disturb them. Surely if your house is a bat nursery and bat droppings are stinking up your house the government would allow removal. I'm just guessing though. You might want to read this article (plus the comments at the end): Emergency Pest Control Ireland: Bats. That company may be able to help you. Good luck!


July 3, 2010 at 2:49 PM  
Blogger Robert said...

We have a large Victorian house in Iowa. The attic is finished but I could hear scratching above the ceiling. Discovered that around 95 bats emerge from the corner of the sofit each night on the SW corner of the house and 45 to 50 on the NE corner. Yesterday we hired a bat exclusion company. They came and sealed all the gaps in the roof area and attached a screen/one way door thing similar to what you described at the main exit/entry. They assured me the bats would exit and couldn't return. I must have asked them 5 times to assure me none would end up in the living areas of the house. They assured me none would. WRONG! At dusk, not one bat emerged at the time they usually do. However, they did start appearing in the house (first floor). Then we discovered they were coming up from the basement. We went down there and saw them in the floor joists and 3 or 4 started flying around. Unfortunately, several got upstairs before we realized we should have had the basement door shut. Now, we have no idea how many are hiding in the first or second floor living areas. There are also undoubtedly many, many in the basement hiding in any number of places. We have the basement door shut and sealed for now. The bat exclusion Co. is 250 miles away and they say this is a worst case scenerio that has never happened before. They did not have any good advice about what to do. They told us they will probably die in a day or two and they will come in 3 days and clean up the dead bats! This sounds crazy to me. What do we do now?? This is the worse nightmare we've ever experienced.

July 22, 2010 at 5:09 PM  
Blogger Jon Maloney said...

Oh no! That's a terrible situation. It sounds like the bats were intimidated by the new attic exit installed by the company and searched for a better way out. They probably found a way to crawl inside the walls to get to the basement. Plus, you don't know if there are babies that can't fly yet still in the attic, or babies that may be born in the basement.

The bats are desperate to find a way out to feed. If your basement has screened vents above ground level, as some basements have, opening one of those might give the bats a way to get out. The problem is that bats will come back in the same hole they exit through. So you would have to set up an exclusion device that the bats would be willing to leave through but would not be able to return through. I would be tempted to remove the exit provided by the company, turn all the lights on in the basement, and hope that the bats discovered they could come and go through the attic opening. Once the bats became used to coming and going through only that hole, then putting an exclusion device in the same place might work.

I'm just sharing some ideas. I am no expert. I agree with you that trying to seal all the bats in the basement until they die sounds crazy. I would check with local experts (perhaps at a nearby college) to find out when the nursery period is over. You should not try to exclude bats until all the babies are old enough to go out feeding. I wouldn't hesitate to check with a different pest-control company for alternatives.

July 22, 2010 at 5:52 PM  
Blogger Robert said...

Update: a couple days later, there were no traces of any bats (dead or alive) in the basement?? Also, all noises and scratching in the ceiling above the 3rd floor ceased. I would like to think they found their way back up and exited the place where the one way screen was placed. I'm hoping they didn't crawl up the walls and die. There was a bucket of water in the basement and no bats had gotten trapped trying to get water so it gives me hope that they somehow found their way out.

July 29, 2010 at 5:14 PM  
Blogger Jon Maloney said...

Thanks for the update, Robert. That's good news. I hope you're right and the bats finally found their way out of the exclusion screen. Good luck!

July 30, 2010 at 1:54 PM  
Anonymous Eileen in Ohio said...

Just found this posting. I had 11 bats last year in a period of a month last year. Live in a 3 story Victorian and they were coming down the 3 chimneys and were getting into my living quarters. Had my 6 fireplaces (2 on each floor) sealed and while doing it found a few hanging from the grates inside (sleeping)! After the fireplaces were sealed had the chimney pots and areas around them wire meshed and none since. REALLY creeped me out as they flew around in my rooms! As I walk my dogs at night I hear them outside and it brings back really bad memories. Know they are good for bugs ~ as long as they stay outside! Your site is great Jon ~ wish I had seen it a year ago. The bats LOVE these big tall buildings. :-)

August 7, 2010 at 8:04 PM  
Blogger Jon Maloney said...

Thanks, Eileen. It sounds like you got your problem taken care of. Some people put up bat houses nearby when they remove bats from their home. It gives the homeless bats a place to live and helps keep the mosquitoes in check. I put a bat house that I bought from the National Wildlife Federation near the roof peak of my parents' house once but I don't think bats ever used it. Maybe the temperature range wasn't to the bats' liking.

August 7, 2010 at 9:09 PM  
Anonymous Anonymous said...

How likely would it be for a bat to fly in an open window during daylight?

August 26, 2010 at 2:11 PM  
Blogger Jon Maloney said...

Just yesterday a friend of mine in Virginia told me he left his patio door open and a bat flew in. He didn't say whether it was day or night.

Bats do fly during daylight, mostly within an hour or so of dawn and dusk. I've also seen them fly at other times of day, especially on unseasonably warm days during cold weather. If it's warm enough for insects to be flying around, then hungry bats that aren't dormant for the winter might be willing to fly and feed.

If a bat flies into an open window or door by mistake, I bet its first instinct is to try to find its way out. A bat wants to get away from you as much as you want to get away from it.


August 26, 2010 at 2:40 PM  
Anonymous Anonymous said...

What do they do when they fly into a house -- keep flying, go hide, ???.

August 27, 2010 at 10:03 AM  
Anonymous Anonymous said...

Kind of a general followup to my last question. If a bat gets into a house, do they remain active enough to know they are there, or can/do they disappear somewhere so you don't know if you have a bat or not?

August 27, 2010 at 10:09 AM  
Blogger Jon Maloney said...

I can't answer your questions with any certainty, but I can make reasonable guesses. A flying bat is likely to be doing one of three things -- feeding, going someplace to roost for the day, or going someplace to spend the winter.

If a bat that is out feeding flies into your house it will try to find it's way back out as fast as possible. If a bat is flying around in your house in the dark trying to find its way out, and you turn on the lights, then the bat might try to hide in a dark place to get away from you and to get away from the light.

I guess it's possible that a bat looking for a roost or for a place to spend the winter could fly into your house, but I think it's unlikely. Bats want a dark, quiet, undisturbed place to roost or go dormant. They would try to avoid the lights and activity of a live-in house.

The lady who lived in the apartment next door to me once found a dormant bat lying in a deep glass dish in her kitchen cabinet. She brought the dish outside and set it on a chair. I was examining the bat when it woke up, stretched its wings, and flew away. The bat didn't get into her dish in the cabinet after flying into her apartment. It crawled from the attic, through the wall, and into the cabinet looking for a cool undisturbed place to spend the winter.

August 27, 2010 at 10:45 AM  
Anonymous Anonymous said...

Good stuff. Any ideas on how to deal with bats in yard? They are eating the berries on two of the trees and getting rid of the tree is not an option. I don't mind the bats but they are pooping all over the exterior of the house and it's starting to get on my nerves. Help!

June 12, 2011 at 10:28 PM  
Blogger Jon Maloney said...

I have only had experience with insect-eating bats. I've never dealt with fruit bats. Common sense tells me that as long as you have a tree with berries the bats like, bats will come to eat the berries. I performed some searches to see how others have handled your problem. You might find some ideas on this forum page helpful: Repelling Fruit Bats/Flying Foxes ? ? ?. Good luck!


June 13, 2011 at 2:29 PM  
Anonymous Anonymous said...

thx for the info. meanwhile, my wife and i are still going back and forth on whether to cut down the tree or not.

June 14, 2011 at 9:22 PM  
Blogger Jon Maloney said...

I thought of another possibility worth mentioning, although it might be worthless for several reasons. Would it be possible to harass the bats by spraying them with a high-pressure stream from the nozzle on a garden hose whenever you saw them feeding? If you did it often enough they might decide to go elsewhere to feed. - Jon

June 15, 2011 at 6:24 PM  
Anonymous Anonymous said...

thx for the idea. i'm open to all suggestions at this time. can i get ur take on why that might be worthless?

June 15, 2011 at 7:41 PM  
Blogger Jon Maloney said...

Sure. It could be worthless because I don't know your situation. You might not have available water under pressure. You may not have a garden hose that will reach the tree. The tree might be too tall. The bats may only feed at night. For all I know you're in the Australian outback. :-) - Jon

June 15, 2011 at 7:49 PM  
Anonymous Anonymous said...'re close. i'm an expat living in philippines at the moment. i do have a pressure washer handy so i'm planning on using that and yes they only feed at night. i tried disturbing them with my airsoft bb gun (5 days now) but so far they don't seem to be phased. they keep coming back night after night. since ur response, i've seen articles on how bats don't like getting wet.....hope this does the trick. thx!

June 17, 2011 at 1:10 AM  
Blogger Jon Maloney said...

Please come back after you've tried it and tell us if the plan worked. Not only am I curious but other people searching for info will be helped too. Good luck! - Jon

June 17, 2011 at 1:27 AM  
Anonymous Anonymous said...

Jon, When we had the roof reshingled, the roofers insisted on putting ridge vent on the roof. I have never had any bats in my attic before, but now i do. I recently found one hiding in my shoe, yes i found him by putting my foot in the shoe and getting bitten. He did not have rabies, thankfully, however we still have many bats in our attic. We have sealed up the ridge vent with the spray in foam that expands and that seems to have helped, however we still seem to have some bats up there. We vacuum up the guano and then look the next day to see if there is more. I cannot find the bat(s), they seem to be hiding up there in my boxes of stuff. How can I flush them out? We have tried putting up netting which they seem to avoid, and have also put down the glue sheets and have caught 2 of them this way. Any ideas will be greatly appreciated. Thanks, Lynne

June 23, 2011 at 5:42 PM  
Blogger Jon Maloney said...

Lynne, The trick to getting rid of bats is letting them get rid of themselves. They need to get out to feed at night. The way to get rid of them is to let them leave to feed, but make it so they can't get back in. That's the subject of most of this blog entry on bats. Here are the basic steps.

1. Watch all the edges of the house at dusk for several nights to identify the openings used by the bats.
2. Seal all except the most-used opening.
3. Over the main opening attach an exclusion device that lets bats out but won't let them back in.

After a week or so all the bats will be gone.

We hired Critter Control to solve the bat problem in my building, and they did a great job.

It sounds like you have sealed the bats in your house, which is what you don't want. If I were you I'd make sure there's an opening the bats can use to leave. The opening should be designed so that bats can't get back in after they have left. If you don't want to try to do it yourself, hire a company that knows how to get rid of bats. If a company wants to use lights, fans, or chemicals, I'd look elsewhere. Those methods don't work.


June 24, 2011 at 7:17 PM  
Anonymous Anonymous said...

jon - spraying water with pressure washer didn't work!! they didn't seem to mind the water one bit. turns out that they even come out to feed when raining!! so much for the bats don't like to get wet theory. but i'm not giving up just yet. any other ideas besides cutting down the tree?

July 11, 2011 at 7:52 PM  
Blogger Jon Maloney said...

There were a couple of ideas in that forum I linked to a few posts back. One poster said hanging CDs on fishing line scares bats away. Here's what he said:

"To solve this Use a piece of fishing line. Put a 3 or 4 CD's (preferably old Michael Bolton or similar LOL) every 30-40 cm and hang nearby. Supposedly freaks them out and they dont come back. 1 or 2 of these will cover the whole back yard."

Other posters talked about using an Australian product called Birdfrite.

Here's a page that talks about using Birdfrite in combination with floodlights to deter fruit bats: About Flying Foxes and our Flying Fox control products.

Good luck!


July 12, 2011 at 9:45 AM  
Anonymous Anonymous said...

Jon - quick we started to do some tree trimming around the yard and my neighbor followed suit. they found one tree, right next to our house, infested with bats!!! so they completely trimmed the tree and now we are 'almost' bat free. still have 1 or 2 bats drifting here and there but at least it's manageable now. i've decided to go back to airsoft gun to try to scare them away. will keep you posted.

July 21, 2011 at 10:01 PM  
Blogger Jon Maloney said...

Thanks for the update. It sounds like the only effective way to deter the bats was to remove their food.

July 22, 2011 at 9:26 AM  
Anonymous Anonymous said...

Well, we had some bat removal guys come out and they put the pvc pipe up for the bats to exit, and after 4-5 nights watching for them, nothing. After a few days of hearing them in that spot, nothing. He concluded they died in our attic, geez. He said they'd turn to rawhide and we wouldn't smell a thing, which we haven't. So they just removed the poop from the attic, and sealed spot around the house. Hope this is the end of them, yikes, From, Kathy, Temperance, mi

August 5, 2011 at 8:47 AM  
Blogger Jon Maloney said...

Hi Kathy, It sounds like your ending wasn't perfect, but overall pretty good. I hope the pest guy was right and that any remaining bats have died. At least the house is sealed now, you don't seem to have any bats, and you don't smell dead bats. Thanks for posting. - Jon

August 5, 2011 at 1:43 PM  
Blogger Sam Howe said...


It looks like you haven't posted for a year but I have a question. I found about 20 bats living in my attic two weeks ago. I've been working in the attic sealing off portions of the roof with roofing tar, the cable company was up there. I went up yesterday and I did a little cleaning and found no live bats and 4 dead bats and one dead bat outside. We have had 2 days of pouring rain and I cut down alot of the bushes behind my house prior to the rain. Do you think that I can seal off my attic if I do not find any bats again today or do I need an exclusion still?

June 14, 2012 at 9:59 AM  
Blogger Jon Maloney said...

Hi Sam, I bet you know what I'm going to recommend. :-) I recommend you set up some sort of exclusion device after you've isolated the main opening and sealed all the other openings. When I had over a thousand bats two or three different men explored the attic and found no sign of any bats. The bats were roosting in the wall and only passed through the attic to get in and out of a hole. So I wouldn't trust not seeing bats in the attic. There's a compromise you could try, but I'm not sure it's any easier. Get several friends or family to surround the house and watch for bats from a half hour or so before dark to a half hour or so after dark. If after a few nights of doing that you haven't seen any bats you may feel more confident in sealing the hole. Of course if you seal the hole and there are bats inside, they'll be forced to seek another way out and might end up in your living space. You should also consider whether there are babies who can't hunt yet. If there are, sealing the hole will trap mothers and babies. If there are babies creating an exclusion system or waiting until cold weather might be your best bets. Good luck!

June 14, 2012 at 3:24 PM  
Anonymous Gail, mi said...

what happens if you do the exclusion method and the babies are inside? I assume the babies will die, but are there other consquences such as smell, or will the mothers damage other things trying to get back to them?

July 26, 2012 at 9:17 PM  
Blogger Jon Maloney said...

Hi Gail,

I can only guess at the answers. It has been my experience that bats are reluctant to leave out an exit that they can't get back in. If they have no alternatives and they're hungry enough, they'll leave. That's why the exclusion setup should stay in place for weeks. My guess is that mother bats nursing babies would be even more reluctant to leave. They may leave after a long time or they may stay inside and die with the babies. Of course whether there would be any smell in the living space of the house would depend on a lot of things -- the number of dead bats, the size of the spaces involved, the air flow. If it was just a few bats I doubt if there would be much smell, plus bats are so small that whatever smell there was probably wouldn't last very long. I have never read anything about bats chewing. From what I've read and what I've witnessed, bats are not destructive.

I hope that helps.


July 26, 2012 at 9:34 PM  
Anonymous Anonymous said...

Wow this was a very interesting post. I found bats flying in the garage in May but didn't call a pest control company until June 1 and they told me that they don't remove bats between June and August because of the babies. I live in Ontario Canada. We needed to have our house reshingled and confirmed with the pest control people that it was okay to do this because they go under the eaves and swoop up to enter in and probably go in through the attic and live in the garage! No one seems to believe me that this is possible that they can crawl through walls unless they've had a bat problem before, anyway the roofers found a hole to the attic where raccoons had gotten in with the previous owners so I had them seal it (it is early August) and I did feel very bad about the bats, so every night I wait outside at dusk (8:50 - 9:15) and watch for bats, first night a baby and I'm assuming the mother came out, 2nd night a big bat and my neighbour saw it, 3rd night another bat, 4th night nothing and 5th night another one! tonight it rained and stormed so I didn't wait but now that I'm reading this I see that they don't go out every night and I'll be doing this for the rest of the summer. I don't want to kill any bats and I'm not even sure that these are not the same ones coming and going except for the baby, I've never seen the baby come out again. Interesting that they come and go all night long, not in this house if the hole was sealed, they only get one opportunity unfortunately. I hope that they do not die up there! I am going to have to go up and check in the attic but the attic grosses me out. Thanks for the story, very educational.

August 4, 2012 at 8:47 PM  
Blogger Jon Maloney said...

That's interesting that your pest control folks refuse to do bat exclusions between June and August because of babies. That's good.

The size a crevice must be for bats to go through is amazingly small -- only ¼ by 1½ inches for some species. One good thing I've read is that bats don't chew structures. They don't damage a house to make an opening larger, for example, like squirrels do.

Good luck with your bats. Thanks for posting!

August 5, 2012 at 1:39 PM  
Anonymous Anonymous said...

Hi - I have found your information very interesting, but my bat problem is one bat that decided to enter my house as someone came in. It flew into a bedroom and I closed the door, hoping to trap it to let it out the window in the evening. Problem 2 - I can't find it anywhere in the room. I know nothing about bat behavior, so I nam trying to find out if bats hide in obscure places during the day and then exit through the open window on it's own. Thanks in advance for any help.

August 5, 2012 at 4:18 PM  
Blogger Jon Maloney said...

I know you shouldn't try to catch a bat in the house or try to chase it out a door or window. You should let it fly out by itself. I found instructions for what to do with a bat in the house on a fact sheet from Cornell University. I hope it helps. Good luck!

August 5, 2012 at 6:48 PM  
Blogger Carol Pouti said...

Very interesting and informative! Tx Jon I am not sure of a bat problem but I am starting to think it may be bats! I found some poop which I though was from a mouse in my utility room where my oil furnance is and my hot water tank etc! I have set numerous mouse traps of different varieties and nothing but more poop on the floor!! There is a vent on the ceiling in this room from the oil stove and of course the pipe on the roof! There was a single bat living in my folded umbrella in my backyard so my brother and I wondered if the bats could be living in this pipe on the roof and the droppings falling from the inside vent from it onto my floor! I sat outside at dusk yesterday and saw a few bats flying around above my house but didn't notice any coming out of the pipe or chimmney! Any thoughts on this?? Appreciate it!!

August 6, 2012 at 9:32 AM  
Blogger Jon Maloney said...

Hi Carol, I think mice and bat droppings can be about the size of small grains of rice. Bat droppings would collect in an area directly under the bat's roost. Mouse droppings would probably be scattered around the floor. You can analyze the droppings under a good light. You might even want to use a magnifying glass. You should wear gloves if you handle droppings. Mice eat grains and other plant matter. Bats eat insects. Finding insect parts in the droppings would make them more likely to be from bats than from mice. You might see leg or wing pieces. You could affix a tray or something under the vent and vacuum the floor. If you later find droppings on the floor they're coming from something in the room. If droppings are on the tray they're coming from the vent. I hope you find those thoughts helpful. Thanks for posting.

August 6, 2012 at 10:03 AM  
Blogger Carol Pouti said...

Great!!!! I'm going to try the tray idea! Thanks so much for replying Jon!

August 8, 2012 at 3:55 PM  
Anonymous Anonymous said...

help! we had a bat control service install exclusion screens today because we discovered we have a lot of them living in our roof and chimney. We found out because we had two in the house - that was last Wednesday. We saw one more on Thursday and then none until tonight when we have seen 5 more. They are getting in somewhere we can't find and the exclusion technique has obviously motivated more than a few to find ways in. The last two were in the bedroom - after we taped and shut everything we could think of so they are entering somewhere in our room, but not just our room, we've found them in other parts of the house when the bedroom was closed off. I don't think there is a safe spot anywhere. I thought if I went to sleep I could ignore them because I thought they would never land on me but I just read several articles that said people can be bitten while they sleep. I don't know what to do. So far my only solution is to completely freak out and wake my husband up so he chases them out- while I hide under the covers. So far it's working for me but pretty sure my husband would like an alternative solution. What should I do???? should we go to a hotel, should I stay up all night? help!!
completely freaked out in wisconsin

August 21, 2013 at 1:01 AM  
Blogger Jon Maloney said...

This comment has been removed by the author.

August 21, 2013 at 12:56 PM  
Blogger Jon Maloney said...

This comment has been removed by the author.

August 21, 2013 at 1:02 PM  
Blogger Jon Maloney said...

You're in a tough situation. I am not an expert, but I can share some analytical thoughts and tips. I assume your main priority is to get the bats out of the living quarters of your house. Bats are entering your living quarters because you put exclusion screens over their normal exits. Bats are reluctant to leave through exclusion screens. They need to get out to feed so they are seeking alternative exits and finding ways into your living quarters. Bats can squeeze through tiny openings, only ¼ by 1½ inches for some species. That means they can probably go under interior doors, through air vents, around pipe openings, around ill-fitted chimney flues, etc. Obviously the bats have found one or more paths into your living space from the attic or chimney. If you remove the exclusion screens then the bats will be comfortable exiting using their normal route and will no longer enter your living space.

As for bats already in your living space, it's better to let bats leave on their own rather than try to chase them out. If a bat is in a room you should open a window to the outside and close the doors into the rest of the house. The bat wants to get out and you want the bat to get out. You need to make it easy for the bat to leave. Stand in a corner or against a wall and watch. Try not to move around to scare or disorient the bat. The bat should fly around the room, find the open window, and fly out.

My suggestions thus far would attempt to put things back the way they were, with bats living in your attic and not in your living area. If you're intent on keeping bats out of your chimney and attic, you can leave the exclusion screens up, but the price will be bats coming into your living area. You said you have tried to seal all the openings from the attic and chimney into the living area, but since the bats continue to get in there seem to be one or more openings you haven't sealed.

I think the best solution would be to leave the exclusion screens in place, find and seal the missed openings into the living areas, help bats out of your living space one by one, wait until winter when the bats have migrated, and carefully seal all the openings into your attic and chimney from outside. This would prevent bats from getting back into your house next spring. Here's a good article you should read by Wisconsin University: Bats: Information for
Wisconsin Homeowners

Good luck!


August 21, 2013 at 1:08 PM  
Anonymous Anonymous said...

When we would get bats in the house they will fly to lights like a moth... so would turn out all lights but one room- then turn light on in a room closer to the door - and off in first room.- continue until last light is porch light with the front door open they happily fly out door ! Easy

December 15, 2014 at 1:34 AM  
Anonymous Anonymous said...

Also do not leave on with garage door with light open at dusk they will fly in to get bugs around the light. Get trapped in garage and may come into living space.

December 15, 2014 at 1:37 AM  
Blogger Jon Maloney said...

Thanks for posting those tips. Perhaps they will help people who get bats in their houses and find this blog looking for help. - Jon

December 15, 2014 at 10:24 AM  
Blogger Elizabeth Hanna said...


Thank you so much for continuing to respond to these. We had a bat drop through our old house into our first floor drop ceiling. It got into our living space pretty quickly and we frantically closed doors and were able to get it outside. We are renting and I'll be talking to my landlord today about this. However, I have a feeling she won't do anything about it. She didn't seem to care there were birds in the eaves. My husband watched last night and saw 4-5 bats exit our neighbor's house. I'm panicking. We have a young child and I'm imagining worst case scenarios. Moving isn't an option this year. What is the harm in just coexisting? We won't live here more than another year or two and our attic access is bolted shut by the landlord. I just don't know how hard I should push for exclusion. Finding another place to live is going to be difficult, but I'm looking!

May 30, 2016 at 7:59 AM  
Blogger Jon Maloney said...

Hi Liz,

It sounds like you don't know if you have a bat problem. A bat found its way into your living space and you helped it escape. Then when your husband watched for bats he only saw some exit your neighbor's house, but not from yours. That's good, not for your neighbor, but good for you.

A bat would not want to be in your living space, so what does it mean that a bat came in? It could mean there are lots of bats in the attic and one accidentally got into your living space. However, if that were the case, then your husband should have seen bats leaving your house at dusk. Since your husband didn't see bats leaving your house, it's probably safe to assume there are not a lot of bats in your attic. If there was just one bat, or very few bats, the most likely reason one got into your living space was because it couldn't find its way outside to feed. That's a good sign. If it's hard for a bat to leave the attic then it's also hard for a bat to get into the attic.

If you want to determine if you have a bat problem you need to have people watch all around your house from about a half hour before dusk to a half hour after dusk for a few nights. Only if you see bats leaving your house will you know if you have a problem. Here are the steps I wrote in an earlier comment.

1. Watch all the edges of the house at dusk for several nights to identify the openings used by the bats.
2. Seal all except the most-used opening.
3. Over the main opening attach an exclusion device that lets bats out but won't let them back in.
After a week or so all the bats will be gone.

Even having a bat inside is no reason to panic. My apartment has no ducts connecting air vents. Instead, it has open space between the upstairs floor and the downstairs ceiling. The central heat and air conditioning blows air into that space and the air comes out of vents in the floors upstairs and ceiling downstairs, but without ducts. During the worst of my bat problem I could hear a bat crawling around in the space between downstairs ceiling and upstairs floor. I never saw it. The bat never dropped down into the rooms through an air vent.

I keep glue boards on the floor under the kitchen counter beside the dishwasher and in the front hall under a trivet stand. The glue boards are just to catch the occasional cockroach or spider that gets in. When I got back from a week-long trip I found both glue boards side-by-side on the kitchen floor. They had bits of dark fur stuck to them. It was clear to me that a bat had gotten stuck to both glue boards and dragged them around before being able to free itself. To this day, many years later, I have never found the bat.

Of course I was a little antsy for awhile after that incident, knowing a bat was loose in the house somewhere, but the fact that I never saw it shows how shy it was. I found some droppings near the water heater and deduced that the bat had left the living space by crawling through a hole in the drywall behind the water heater where wires came through. I assume the bat crawled into the wall and died. Anyway, the point of that story was that even if a bat gets in, it is more afraid of you than you are of it. It will leave if you give it a way to leave.

Good luck!


May 31, 2016 at 3:16 PM  
Blogger Elizabeth Hanna said...

Thank you so much! We got out of the house for the night. I'm much less jittery now. My husband talked to the neighbor and they have large piles of guano in their attic. They rent too and don't seem to care. So I'm hoping ours was just a little lost guy that went down the wrong chimney. My landlord said she wouldn't have a clue as to what to do. I told her I'd let her know if it happened again. We'll set up a watch and see what happens.

Thank you again for your response!

June 1, 2016 at 6:11 AM  
Anonymous Howlin John said...

Thanks for the great advice! About six weeks ago I installed a bat tube made from a straight piece of plastic gutter at an exit point 1in gap where 9in soffit meets chimney. My question for you is: Can I conclude that my bat tube is working solely because I saw approx 10ea bats exit the tube in first hour post sunset after install? Gave up at the hour mark but I could still hear some brushing up on the proximal end of the tube. It took awhile for each bat to jostle, scratch and drop down the tube while I was observing. There haven't been any in the home since install, but I think that I still hear something up in the attic once in awhile. Just wanted to know your thoughts on if my bat tube was working. Thanks again!

June 2, 2016 at 11:04 PM  
Blogger Jon Maloney said...

Hi Howlin John,

You asked, "Can I conclude that my bat tube is working solely because I saw approx 10ea bats exit the tube in first hour post sunset after install?" The tube has two functions — to let bats exit and to keep bats from entering. Your seeing 10 bats exit means it worked for some bats as a way out, but you don't know if they're also using it as a way in. Also, my experience is that most bats don't want to exit where they won't be able to get back in. When the professionals set up the tube on my building, some bats refused to go down it and instead found another way out under a shingle at the corner. The pest contractors sealed the gap under the shingle and left the pipe up for several days or weeks afterward.

My advice to you is to watch all around your house's roof from about a half hour before dusk until about a half hour after dusk. If you watch several nights in a row and no bats come out, then it might be safe to remove the tube and seal the hole. I say "might" because it's possible you missed bats exiting.

Good luck!


June 3, 2016 at 3:03 PM  
Anonymous Linda said...

Great information. This past week, I have had several nightly visitors in my house. I have checked the outside and don't seem to find any access points, but have plugged suspicious sites. Question: could it be possible for bats to come down my chimney, which has no screen, into my furnace and duct work to exit thru the registers into the living quarters? Or, can it possibly be that a bat will come and go thru an open doggie door. I will continue to watch for bats exiting at dusk, but so far none that I can see. I do see bats flying at night/dusk but not a large number. Don't mind bats, but not in house.

August 5, 2016 at 12:13 AM  
Blogger Jon Maloney said...

Hi Linda. If you had several bats inside your house in one week, then there must have been an attractive way in. Of course I have no idea how your chimney and furnace are configured, but if your chimney is attractive and bats fly in and then for whatever reason can't find their way back out, they will seek a way out which could lead them anywhere that's accessible. If they get into your duct work then, yes, they could come into your living space through vents. They wouldn't want to though. It would be an act of desperation trying to find a way out. Of course a bat could come through an open dog door, but why would it?

I can share what I think about bat motivations. I'm going to assume you're in the US and it's warm summer where you are. I think bats will only come inside a house for one of three reasons — by accident through an open window or door while flying and feeding, to find a dark safe place to roost for the day, or to find a dark safe secluded warm place to have and care for babies.

It's unlikely you had several bats come in by accident. However, it's also unlikely that a bat looking for a place to roost or for a place to have babies would voluntarily enter your home's living space. Bats avoid people if they can. I had a bat loose in the air space between the second story's floor and the ground floor's ceiling. There is no duct work connecting the air vents. The bat only came into my living space when I was out of town for a week. When I got back the bat had moved two glue boards around on the floor and left bits of fur on them. The glue boards were not strong, like for mice, but for cockroaches and other bugs. Although I searched, I never found the bat and it never let me see it. Bats are shy and will avoid you if they can.

I don't know what's going on at your house but I can make some suggestions of what to do if you're eager to do something. Watch around your roof for about an hour at dusk for a few nights in a row. Pay particular attention to the chimney area. If you see no bats exiting your house you could put a screen over your chimney. If I remember correctly some bats can enter holes as small as 1 inch by ¼ inch, so the screen should have small holes. If you block an opening the bats are using and there are bats inside, then the next time they try to leave they may find their way into your living space. If the dog door opens into a room that is often dark at night, you might want to leave a light on in that room.

Good luck!

August 5, 2016 at 2:24 PM  
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December 17, 2017 at 4:26 PM  
Blogger Jon Maloney said...

This blog is hosted by Blogspot, which is owned by Google. Blogspot is good about recognizing spam and not publishing it. Every once in a while I log onto Blogspot and check the comments that have been added since the last time I checked. If any spam has been published I delete it. If any legitimate comments have been held as if they were spam, I publish them. It's not hard.

December 18, 2017 at 10:10 AM  
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