How to safely remove bats from your home

I’ve always been a fan of the local bat populations. I’ll admit, some of my admiration comes from their ability to consume bugs, but it’s more than that.

The varieties we have locally — big and little brown bats — can consume up to 1,000 mosquitos an hour. Don’t get me wrong, that’s impressive, but bats are so much more than flying rats that eat thousands of bugs every night. In fact, many don’t realize they are more closely related to humans than they are to rodents. Some research has even suggested certain varieties actually descended from early primates.

Bat species account for a quarter of all mammal species. They range in size from the smallest, the bumblebee bat of Thailand, weighing about as much as a dime, to the largest, the giant flying foxes of Indonesia, with wingspans of almost six feet.

Circling back to the benefits of their diet alone, Farmers are directly impacted. A colony of 150 big brown bats can protect farmers from over 33 million rootworms each summer. They also eat many crop-damaging insects, including cucumber beetles, June beetles, stink bugs, leafhoppers and corn worm moths. Additionally, some crops rely on bats for pollination and seed dispersal.

Unfortunately, many species are becoming endangered due to their slow reproduction rates and habitat loss. Around 40 percent of American bat species are in severe decline or listed as endangered or threatened, but their plight stretches across the globe.

Bats make people nervous from a number of reasons — the way they look, the way they move, fear of rabies. People make bats nervous, too, for a number of reasons — the way they look, the way they panic and throw or swing objects at them.

Although both species would probably be happier separate, habitat destruction has created an impasse. The bats that once housed themselves in hollow trees, suddenly have nowhere to go. This is the reason your attic has become so ideal.

You probably don’t want to host a bat colony, and they’d probably prefer a more secluded space, but circumstances have brought you together. Before you do something rash, panic and wipe them out, consider all the good they do and give them another option. Maintain the local bat population, and clear out your space.

Bats in homes

As it happens, now is the perfect time of year to help maternity colonies relocate. They start to disperse in late summer and early fall once their pups can adequately feed themselves. The earliest it’s safe to remove a colony is August because pups are confined in the roost until they are old enough to fly.

Single bats in the house. Incidentally, single, wayward bats that find their way into your house are usually pups that are just beginning to fly. Use these tips if an inexperienced flyer makes a wrong turn into your home:

• Try to confine the bat to as small an area as possible.
• Open all windows and doors leading outside.
• Make sure your pets are out of the room, the lights are on and stand quietly against the wall.
• Don’t try to herd the bat towards an exit, or panic and swing something at it.
• Within 10 to 15 minutes the bat should have it bearings and find the exit on its own.

Bat exclusion

Bat exclusion is a safe way to relocate a colony without threatening its survival. It’s a simple inexpensive process to identify entrances, seal holes and provide an alternate roost, or bat box. Follow these guidelines from Penn State Extension:

1Bat watching. The first step is to identify any access points the bats have to enter and exit your home. You spot these entrances by watching for the bats coming and going, or by looking for bat droppings on the outside of your house.

Look for places where joined materials have warped, shrunk or pulled away from one another. Common places to check are louvered vents with loose screening, at the roof peak and in areas where flashing has pulled away from the roof or siding.

2One-way doors. After you’ve located the bat entrances, you need to install one-way doors. One-way doors are pieces of mesh or screening placed over an entrance, forming a long sleeve or tent. These doors will allow bats to exit, and prevent them from re-entering. This method works because bats use their sense of smell to locate their entrances. They will exit the mesh tent and the bottom, but land on top of it near the hole, trying to re-enter.

It’s not wise to install one-way doors until the pups have reached maturity and won’t be stuck in the roost without their mothers. Never install a one-way door during May through August, or young bats will be trapped inside and die.

Installing one-way doors

An easy-to-install one-way door, designed by Dr. Stephen Frantz of the New York Department of Health, is described below:

1. Choose 0.25- to 0.5-inch wire screening or heavy plastic mesh to cover all points of entry. Cut the screening so that it covers the width of the hole and extends three feet below the hole. The screening should project three to five inches clear of the hole so that the bats can crawl between the screen and the building to exit at the bottom.
2. Secure the mesh at the top and sides with duct tape or staples and leave the bottom open.
3. Leave the door in place for at least three to four days, or until you are sure all the bats are gone.

3Sealing cracks. Once the bats have vacated, remove the one-way doors and permanently seal the all of the openings. Use window screening or hardware cloth to cover vents or large cracks. You can use expanding foam insulation or caulking compound to fill in smaller cracks. You may also want to install chimney caps on any chimneys you may have.

Bat houses

Before removing a maternity colony from your home, be sure to provide an alternate roost. Exclusion can be very stressful for a maternity colony because they roost in the same location year after year. Without somewhere to go, they will be forced into a nearby building or house where they could face displacement, extermination or a pre-existing colony. If the colony is killed or forced out of the area, it will directly impact the local bat population.

With a bat box, you can take advantage of the bats’ ability to control insects, while contributing to the protection and management of these beneficial mammals. You can purchase a bat box online or at a home improvement store, or you can construct your own.

Related content

• How to bat-proof your house
• How to build a bat house

Resources

• Penn State Extension