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Bat frequently asked questions

Little brown bats in bat house.
Little brown bats in a bat house. © Heather Kaarakka, Wisconsin DNR.

Below are some commonly asked questions about bats. This is not an exhaustive list. If you still have questions about bats or the bat program in Wisconsin, please feel free to contact the program by emailing DNRbats@wisconsin.gov.

I have bats living in my home, what do I do?

Little brown bats and big brown bats are commonly found roosting in buildings and do find their way into attics and walls of homes. In order to get the bats out, an eviction or exclusion should be completed as bats in Wisconsin are protected and it is illegal to kill them. Eviction involves installing one-way doors that allow the bats to leave but not re-enter the building. One-way doors can be made of plastic or screening but must not cause harm to the bats.

More information on conducting an exclusion yourself

There are many nuisance animal control operators in the state who will do bat exclusion for a fee if you cannot or don't wish to exclude the bats yourself.

Also note that exclusions may not be completed June 1 through Aug. 15 every year to protect flightless baby bats.

I need to exclude the bats from my home during the non-exclusion period (June 1-Aug. 15) because I feel the bats pose a health or safety risk to me or other residents in the home.

Cave bats in Wisconsin (including little brown and big brown) are listed as state-threatened and covered under a Broad Incidental Take Permit/Authorization (BITP/A). All bat exclusion activities are automatically covered under this BITP/A except those occurring June 1-Aug. 15. However, if the landowner deems the bats in the home are posing a health risk (bats routinely entering living space, for example), the landowner may conduct the exclusion provided they fill out and submit the Health Exemption Form. The landowner must complete and submit the form within five days of start of exclusion work. This is not an additional permit, and no response from bat program staff is required once the form is submitted.

*Having trouble viewing the Health Exemption Form in your internet browser? Save it to your desktop by right-clicking the link and then choosing "Save target as..." or "Save link as..." Then open the desktop file by right-clicking the icon and selecting "Open with," and then choose Adobe Reader. You can also try opening the form in a different browser, like Internet Explorer.

I have a live bat flying around my house, what do I do?

Bats occasionally find their way into living spaces, especially in late summer as bats born in June learn to fly and find their way into odd situations. Bats do not want to be flying around inside your home. The safest course of action is to close the bat in a room with a window or door to the outside. Leave the door or window open and allow the bat to leave on its own. If the bat does not leave on its own, wait until it tires and lands. Wearing gloves, use a cardboard or plastic box to cover the bat. Gently slide a piece of paper or cardboard behind the bat and enclose the bat inside the container. Take the container and bat outside and place the container on its side at the base of a shrub or other protected area. Allow the bat to leave on its own. Never throw a bat into the air to encourage it to take flight. Removing a bat from your house

A possible bat-human interaction occurred and I need to know what to do about possible rabies exposure.

If you believe a possible bat-human or bat-pet interaction has occurred, please visit this CDC webpage – Coming in contact with bats.

Bats are roosting under my eaves at night and leaving guano. Is there a way to discourage them?

Bats leave their day roost each night in the summer to forage for insects. After feeding for several hours, they use warm, protected areas to rest and digest for some time before foraging again. These temporary roosts are called night-roosts. Unfortunately, it is difficult to exclude bats from these areas because there is no small opening where the bats come and go. A number of deterrents can be tried to discourage bats from roosting in the area. See page 6 of Bat Conservation International's exclusion guidelines. Pet-repellents, balloons, fans or bright lights may be tried provided they are installed when the bats are not present.

Any attempts to discourage the bats must not cause harm or death of the bats.

I found a dead bat, do you want to know?

Yes, dead or sick bat reports help the Wisconsin DNR bat program track population trends in bats. The bat program coordinates a sick/dead bat reporting system where we are automatically alerted to submitted reports. Report a sick or dead bat

Never handle a sick or dead wild animal without proper protection. Instructions on dealing with dead bats are available on the sick/dead bat reporting form.

If you find and report three or more dead bats found at a single time, you may be contacted and asked to save one or more of the carcasses in the freezer for testing the cause of mortality.

Note that bats awaiting submission for rabies testing must be refrigerated, not frozen. Any possible exposure to the bat (bat flying around and injured/killed by a pet, for example) should be discussed with your pet’s vet if the pet was exposed, or your physician in cases of any possible human exposure.

There is a bat still at my summer roost in late fall, should I do anything?

Normally, bats leave their summer roost sites starting in August, and the colony will have moved to winter habitat by October. Occasionally, if the weather remains above 40 degrees during the day, big brown bats may stay active into November and even December. If you observe a bat roosting or an active bat in late fall or early winter, it is most likely still taking advantage of warmer weather before going into hibernation. It is usually best to let wild be wild in these situations, and not disturb the bat. If conditions are below freezing consistently and the bat is still roosting, please contact a local wildlife rehabilitator who can take care of the bat for the winter.

I have a bat hibernating in my attic, what should I do?

One species of bat in Wisconsin, the big brown bat, is known to form very small colonies that hibernate in buildings in winter. Big brown bats are hardy and can tolerate cooler and drier temperatures than other species. As a result, individuals or small colonies are sometimes found hibernating in attics, insulated barns and garages. If possible, leave the bat alone to continue hibernating until spring. The bat is in torpor and will not usually be active unless disturbed by a change in conditions. If the bat must be removed, please contact a local wildlife rehabilitator who can take care of the bat for the winter. The bat will be released in spring near the place of capture.

Bats are returning to my bat house in January, or I found a large number of dead bats outside in winter.

Large numbers of dead bats in winter or bats returning to summer bat roosts such as bat houses can be signs of the deadly bat disease white-nose syndrome. White-nose syndrome causes abnormal behavior in bats and they are sometimes seen flying onto the landscape in mid-winter and during the day, or dying in large numbers as they leave the infected hibernaculum in winter.

If you encounter either of these behaviors, please submit a sick/dead bat report or contact bat program staff for the next steps. Depending on your location, you may be asked to save some of the carcasses in the freezer for further testing for the disease.

I have heard about a bat disease, what is it?

In 2006, a fungus was discovered growing on the muzzles and wings of hibernating bats. As the fungus spread, it left in its wake a massive number of dead bats. The disease caused by the fungus is called white-nose syndrome (WNS), and it causes mass mortality in hibernating bats. Up to 99% of bats can die in an infected hibernaculum. The fungus is genetically identical to one found growing on bats in Europe, so it is thought that the fungus crossed the Atlantic Ocean. The exact mechanism of mortality is unknown; however, infected bats have low body weight, damaged wings and are dehydrated when they die. The U.S. Fish and Wildlife Service has estimated over 6 million bats have died from the disease since it was first discovered in 2006, and the regional extinction of the little brown bat is expected in several areas. WNS was first confirmed in Wisconsin in March 2014 and has since spread to eight counties. Learn more about white-nose syndrome

Why should we protect bats?

Bats in Wisconsin are insectivorous and are major predators of night-flying insects including agricultural and forestry pests. A single bat can consume up to 1,000 mosquito-sized insects in an hour, and a pregnant female can consume her weight in insects every night. It has been estimated bats save farmers in North America over $22 billion every year in pest control services.

Bats are long-lived, slow to reproduce and often concentrate in large numbers in summer and winter. Bats can live over 25 years and usually have only one baby, called a pup, per year. As a result of this life history, bats are very susceptible to drastic population decline such as that caused by white-nose syndrome. Recovery to pre-WNS population levels may never occur.

What is Wisconsin doing about white-nose syndrome?

For over seven years, the DNR bat program has been inventorying and monitoring bat populations across the state. This is done through a combination of volunteer effort, surveying summer bat colonies, conducting acoustic surveys and on-the-ground fieldwork of bat program personnel. Thanks to these efforts, Wisconsin has baseline information about where bat populations are, what population levels are normally found at each site and what is considered normal bat behavior prior to WNS. This information helps the bat program track WNS as it spreads through the state, provides the opportunity to study the disease and possible treatment options and helps further the understanding of the true impacts of WNS.

Is there anything I can do to help?

Yes, there are several ways to help conserve and monitor bats in Wisconsin. The bat program coordinates two citizen-based monitoring projects assessing bats in the summer – acoustic and roost monitoring. Learn how to become a volunteer

Acoustic monitoring involves being trained to use an ultrasound detector that records bats as they navigate and forage. The recordings can be analyzed in the office and just like a bird can be identified to species by its call, bat species can be identified by their echolocation sonograms. This project helps assess species distribution in the state and look at the relative abundance of bats in different habitats.

Roost monitoring involves finding and monitoring a summer bat roost by counting the bats as they emerge in the evening to forage. Bats often congregate in bat houses, bridges, barns and other buildings and are reported to the bat program by volunteers or landowners. Conducting emergence counts of these colonies helps the bat program assess population levels at each site and investigate roost behavior and roost conditions of bats. The bat program can still use reported information about roost locations even if the landowner is not monitoring. You can report a roost by emailing DNRbats@Wisconsin.gov.

Donate to the bat program to help continue research and mitigate habitat loss of bats. There are two ways to help the bat program continue to work preserving and monitoring bats in Wisconsin – donate to an endowment or donate to an immediate-use fund. The endowment fund was created by Dave Redell and the Natural Resources Foundation of Wisconsin to help fund bat preservation work in Wisconsin in perpetuity. The immediate-use fund is managed by the DNR's Bureau of Natural Heritage Conservation and is used to help current work such as disease surveillance, gate and bat house installation and bat research. Donate to support bat conservation in Wisconsin

Build a bat house! Building and installing a bat house on your property is a great way to offer alternate habitat and encourage these beneficial animals to take up residence. Bats need warm protected areas to rest during the day and raise their pups. Learn how to build a bat house

Spread the word about how interesting and important bats are. One of the main threats to bats is misunderstanding. There are many myths and misconceptions about bats, and most are negative, leading to fear and disgust of bats. By educating and talking to people about bats, we can slowly change the way people think about these critical animals.