According to the Wisconsin DNR, “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 provide invaluable benefits to our ecosystem, particularly eating insects. According to our DCHS licensed rehabilitator Paige Pederson, “Not only are bats vital to our local ecosystems, many of our Wisconsin bats are threatened species. Since 2014, a deadly fungal disease called White-nose syndrome has been plaguing our local bat populations making their conservation a top priority.” One such threatened species is the Big Brown Bat. The one pictured above was rehabilitated at DCHS's Wildlife Center.
Would you prefer not to be eaten alive by little pests during evenings on your porch? “Bats are fabulous at controlling mosquito populations,” says Paige. “You can attract bats to your home by installing a bat house.”
However, you probably don’t want bats in your home.
We’re now entering the perfect time for bat exclusions, a method to legally and humanely remove bats from your house. Humane methods of bat exclusion typically involved installing one-way doors that allow bats to leave your house, but prevent them from getting back in. Per Paige, “Every bat saved by utilizing humane exclusion methods is a cause for celebration!”
Why is this the perfect time for bat exclusions? In late August, young bat pups are finally raised to adulthood, meaning they are no longer at risk of becoming stuck in a house without their mother. If bat exclusions take place earlier than that, there’s a high likelihood that bat mothers will get excluded from the house while their pups are still trapped inside. The bat pups could starve, and bat mothers will go to extremes to get back in to their babies, almost certainly creating a more difficult situation for you to deal with than you had originally. To protect bat pups, the Wisconsin DNR does not permit bat exclusions to take place between June 1st and August 15th.
But now that we’re well past August 15th and bat pups are able to fly on their own, it’s safe to begin bat exclusions. Furthermore, bats right now are still quite active, so they will exit their roost each night to hunt. With your bat exclusions installed, they can easily leave your house to go hunt, but they will have to find an alternative place to roost and hibernate for the winter.
Note that bats should not be excluded during winter months as it is too cold for them to survive outside.
Want to get started on your bat exclusions? Here are the basic steps outlined by the Wisconsin Aquatic and Terrestrial Resources Inventory:
1. Find out how and where the bats are getting into your house.
As the sun sets or just before it rises, watch your house to see where the bats leave from. Ideally, get some friends to help you, and make sure all of you are able to see the whole structure without turning your head. Bats can leave and fly off in a matter of seconds. Observe for several nights to make sure you can identify all or most exit-points. You can also look for bat droppings or staining caused by bats’ body oils.
2. If you’d like the bats to stick around your property (and really, why wouldn’t you?), build them a bat house.
Clearly, they already like your area, so you can transition them to their own home by offering them a different place to roost. If you build the house a year before beginning the exclusion or at least towards the start of the summer, then the bats should become familiar with the structure as they come and go. If they’re familiar with it, they’ll be more likely to roost there.
3. Install your one-way doors, wait one week, and seal the holes.
You can create your own one-way exclusion devices with a variety of materials: plastic netting with mesh one-sixth inch or smaller, plastic sheeting, or PVC pipe. Regardless of the material, the process is the same: Cover the opening in your home entirely, but let the netting or sheeting extend another two feet below. Secure the top and side edges of the netting or sheeting with staples or duct tape, and leave the bottom edge open so that the bats can escape through it. If you use PVC pipe, insert a portion of it into the opening, and seal the opening around the outer rim of the pipe. Allow the bats five to seven days to leave. Once they have all left, you can seal the openings permanently with the appropriate construction materials. Bats won’t chew their way back into your house, so once you’ve sealed all openings, they won’t be coming back in.
If you’d prefer not to do the exclusion yourself, there are professionals who can complete the exclusion for you. Make sure you find one that deals specifically with bat removal, and will do it legally and humanely.