Bats love chimneys — they’re dark, secluded and offer enough space for them to hang upside down. Humans are less thrilled when we discover bats in our homes, but they’re not as bad as you might think. While bats can pose some health risks, including rabies, they can usually be safely evicted and rarely cause problems.
Removing bats from your property includes a process called exclusion, or allowing them exit, without allowing re-entry. Many species of bats are protected, so it’s important to exclude them properly and without harming them.
Why are Bats in my Chimney?
Chimneys are very appealing to bats, especially in communities where caves are sparse. Bats have evolved to rest hanging upside down to take advantage of spaces like this that most other animals can’t use for roosting.
The fact that chimneys happen to be attached to a human dwelling doesn’t seem to bother them too much. And while they don’t really cause much structural damage, close contact with bats and their feces, or guano, can carry risk of infection. Here are a few of the diseases they carry.
Histoplamosis. Histoplasmosis is transmitted through breathing in histoplasma fungal spores that grow in guano. Symptoms include fever, cough, and fatigue, and most people who get sick don’t require medical attention. Severe cases can occur in people with weakened immune systems, however, and in these cases a doctor should be consulted.
Rabies. Bats, along with raccoons, skunks, and foxes, are considered primary carriers of rabies. The rabies virus attacks the central nervous system and can be fatal if not treated immediately.
A rabid bat can transmit this virus to people through a bite. The virus can also be transmitted through direct contact (through the mucous membranes of the eyes, nose, and mouth) with the saliva of an infected animal.
Fortunately, the chances of being bitten by a rabid bat are relatively low, which means the chances of contracting rabies from a bat are also low. And only 5% to 10% of bats that are tested, test positive for rabies.
Ebola. Bats, specifically fruit bats, can also spread Ebola through direct contact with an infected animal. The Ebola virus is a rare, but often fatal, disease, whose symptoms can mimic those of other diseases like, flu, malaria, and typhoid.
Recovery often hinges on early detection and quality supportive clinical care while your body fights the disease.
The easiest way to avoid being infected by a disease bats carry is to avoid close contact with them. If you have guano close to your home, you should do your best to keep it cleaned up so that histoplasma fungi don’t grow.
5 Steps for Bat Removal and Exclusion
Removing bats from your home is actually more about keeping them out once they’ve exited for the evening, and it’s called exclusion. Because many bat species are protected, you can’t simply trap and kill them. Instead, you seal up the area they’ve been roosting in so they can’t get back in.
Here are five steps to help you properly, and legally, exclude bats.
1. When can I Start Excluding Bats?
Bats are an important part of the ecosystem, keeping insect populations in check. Unfortunately, they have low birth rates, which means that any loss of pups in the spring can cause significant decreases to their populations. Which is why many bats are protected — it may actually be illegal for you to kill them depending on where you live.
Bats mate in the fall, hibernate during winter, and then give birth in the spring. And bat pups are not able to fly for the first few months of their lives. If you start your exclusion process before they’re independent of their mothers, you could be stranding pups inside your house to die of starvation.
To avoid inadvertently killing pups, exclusion needs to be done in the fall, well after pups have been birthed and should be flying on their own. There is also a small window in early spring (before May), before pups are born, that you can start exclusion. If you’re unsure of the timing in your area, contact a professional — they’ll be able to advise you on timing as well as best practices.
2. How are Bats Getting in and out?
The most obvious access point if you have bats in your chimney is going to be the top, but you’re going to need to inspect your house for any cracks or holes 1/2 inch or larger. This includes gaps where your chimney meets the roof, roof tiles, and even siding.
If you start your inspection about 15 minutes before sunset, when bats are venturing out for the evening, you can more easily spot their exit points. Enlisting a few volunteers to watch different sides of you house can help make sure you don’t miss any spots.
Another way to identify entry points is to look bat guano as well as stains from bats’ body oils. Finding guano can help you pinpoint some access points.
3. How to Install Exclusion Devices
Your next step is to install exclusion devices — these are little tubes and flaps that allow bats to exit, but don’t allow them back in. There are different types of exclusion devices, some plastic, some with netting and you can find them at your hardware store. You can also create your own devices, but make sure you know what you’re doing so you avoid injuring the bats.
Tube exclusion devices need to be 2 inches in diameter and at least 10 inches long. They’re usually made of PVC or other smooth plastic so the bat can’t climb back up. The bottom is left open and bats can exit but not re-enter.
Flexible plastic netting devices should be stapled to the surface of exterior walls and extend 18 to 24 inches below the lower edge of the opening. The sides and top should be secured and the bottom left open.
You’ll need to properly attach your devices to all openings, following all user instructions and making sure there aren’t any gaps. Leave exclusion devices on for 5 to 7 days to ensure all bats have exited. Not all bats will leave at the same time, so you need to give them time to exit before sealing openings, otherwise they’ll be trapped inside to die of starvation.
4. How to Prevent Bats from Getting back in
Once you’ve properly excluded bats, you need to seal your openings so they can’t get back in after the exclusion devices are removed.
Caulk and fill entry points, including small cracks and gaps in brick, siding or roofing tiles. You should also install a chimney cap to keep bats from entering there. Make sure you use quality materials that will last. It’s an investment against future unwanted winged visitors.
It’s possible bats will still be trying to return at this point, so keep your windows and doors shut. If they’re just not moving on, you might consider installing bat boxes.
Fun Fact. Bats have a great sense of direction and will continue to return to their roosts even when captured and released great distances away — which is why simply moving them without sealing access points isn’t an effective means of removal.
5. Keeping Potential Roosting Spots Bat-free
When your chimney is once again bat-free, you’ll need to have it cleaned and inspected. Regular maintenance will keep your chimney properly sealed off and allow you to spot signs of possible roosting early on.
It’s also important to remove bat guano from inside your chimney as well as any that’s been left around your property to prevent disease. It may be advisable to hire a professional for the cleanup, but you can also do it yourself.
If you decide to clean your chimney yourself, wear a face mask, gloves, and protective clothing to avoid direct contact with droppings as much as possible. Scrape off guano from the chimney walls and then use a vacuum to collect the droppings. You’ll then want to scrub the area clean — there are commercially available products that help break down any dried droppings you weren’t able to scrape off.
Once you’re done, wash your clothes and equipment. As a precaution, look out for early signs of histoplasmosis such as cough, chills, fever, and breathlessness, among others.
Despite your best efforts, there may still be carcasses to deal with. Apart from the offensive odors accompanied by decomposition, if left inside your chimney a bat carcass can attract flies, maggots, rodents, and other pests.
It’s unlikely that you will contract rabies from contact with a deceased bat, since infection requires direct contact with saliva, but glove up when handling them anyways. And if you think you’ve been exposed to rabies, call your doctor.
If you don’t think you’re up to the task of cleaning out a newly vacant bat roost, you can always call a professional.
Bat Repellents
Certain bat repellents and harassment techniques can be used in combination with exclusion to convince bats to leave the area. These can include ultrasonic devices and the use of bright lights and noise to make the area inhospitable to the bats, without actually harming them.
Bats like to roost in dark, quiet and protected places. If you can make that area of your house bright and noisy, you might be able to convince them to choose an alternate location — like a bat box. You can start by hanging a mechanic’s drop-light (with a fluorescent bulb to reduce heat output) in their roost and placing a radio or fan nearby.
Turn the light on (but keep it away from flammable objects) and play the radio or turn on the fan just before dark. Keep them going all through the night and day. You can use an ultrasonic device in small, confined spaces.
This kind of harassment can push bats further into your house, in search of dark and quiet, so make sure you’ve blocked access without blocking their exits. And you’ll still have to install exclusion devices.
When to Call a Pro
If you have a large colony of bats living in your chimney or other parts of your house, or you’re not sure about safely and legally excluding bats, you might be better off calling a professional. Pest control companies or animal control will be able to help you carefully and legally remove and exclude bats.
Bats can be easy to miss, since they don’t chew or otherwise cause structural damage to walls or wiring like rats and mice do. A professional can make sure that all of your entry and exit points have been properly identified, meaning you’re less likely to miss a roosting area.
Should I Install a Bat House?
Living side-by-side with bats is actually not as bad as you might think. Bats eat up to 6,000 insects on any given night and they’re also pollinators — and they rarely cause problems when left alone.
Providing bats with boxes can give them an alternative to roosting inside your home. And don’t worry, putting a bat box up won’t encourage them to also roost inside your house.
Some bats prefer man-made structures because of the warmth they provide, so bat boxes should mimic those conditions. If there are bats in your area they’ll notice them as they pass by. You can buy or build bat boxes, but they should have a few basic things.
Size matters. Bat boxes need to be at least 2 feet tall and 14 inches wide or larger. Bigger is better. It should also have a 3 to 6 inch landing platform below the opening for the bats to climb up. The inside can have either a single chamber or multiple chambers but they need to be 3/4 to 1 inch wide.
Well constructed. Because the box needs to be capable of trapping heat, it needs to be screwed together and caulked to prevent gaps that might let out heat or let in drafts.
Painted black. It also needs to be placed in a sunny spot on its own pole or on a southern- or eastern-facing exterior wall of a building so it can absorb heat during the day. Bat boxes should not be placed on trees, since they’ll end up in the shade and also in close proximity of owls and other predatory birds.
And make sure you place bat houses away from areas where they might be disturbed during the day. Installing them about 20 feet off the ground will usually do the trick, but you should account for ambient noise, like traffic as well. Placing them toward the back of your property and away from busy streets can help with this. This will also keep their droppings from bothering you.
Finding bats in your chimney is no reason to panic. By following the above steps for proper exclusion and exercising caution, you can avoid most problems. Bats are an important part of the ecosystem and can be helpful insect eliminators — you may want them nearby, just not necessarily in your chimney. Just make sure you’re aware of all local laws regarding bats and do your best not to harm them. If you find yourself needing help, call a professional.