Bat Exclusion

The long-term solution for bats that enter buildings and cause a nuisance problem or present a public health hazard is systematically repairing the structure. Chemical toxicants never solve house bat problems and often create different, more dangerous problems. This section describes bat-proofing techniques that when used in conjunction with an effective bat box will effectively deal with house bat problems. Recent declines in bat populations and a greater appreciation of the ecological importance of bats have led to this solution which encourages bat conservation, protects human health, and permanently solves nuisance problems.

Table of contents

Summary

  1. Observe your building around sunset or sunrise to detect all locations bats are using
    for access.
  2. Install a bat house prior to conducting exclusion in order to maintain the beneficial
    insect‐eating service of the bats in your backyard.
  3. Install a one‐way door over the opening(s) and wait a week until all of the bats have
    left.
  4. Permanently seal the access points with appropriate materials.
  5. Enjoy a night on your deck or patio and watch your relocated colony of bats eat
    100’s to 1,000’s of mosquito‐sized insects.
  6. Let us know how it worked out as we would like to hear your success story about
    relocating bats from your attic to their own bat house.
  7. For additional information on bats of Wisconsin check out our bat website. Source

Devices For Bat Exclusion

  • 1/4 inch poly netting – a good all-purpose bat net with a small enough grade to prevent the bats from getting stuck in the mesh or strangled. It must be set correctly though, to allow the bats to fly out but not fly back in. Making this shape right is an art, like a sculpture. I usually set netting on long gaps with clear exit routes. Sometimes you have to extrude the net with brackets to allow enough clearance for the bats. They won’t exit the building if there’s an obstruction in the way.
  • Window Screen – yes, regular window screen at home depot, the softest you can find, makes a great exclusion tool (as seen in the photo above). As with the netting, a combination of staple gun or duct tape is a good way to secure it to the house. I usually use screening on smaller gaps adjacent to flat surfaces. Make sure there are no gaps on the edges that allow the bats back in!
  • Funnels – funnels made of various materials, from clear plastic to 1/4 inch steel screening, work very well in some scenarios. Even a small water bottle, cut open at both ends, can work! I don’t use funnels if there are a lot of bats, because of the bottleneck (figurative, not literal, the neck of a bottle would be too narrow). Funnels are best used in areas with horizontal or tricky architecture when the bats are leaving out of a small hole.
  • Bat cones – these are special funnels with a tapered body and attachment wings that you can purchase online.

Home Inspections For Bat Entry

You need to find out where the bats are getting in and out of the house, where exactly they are living, what type of bats they are, and the damages they have caused. You can start by standing outside your house at dusk and observing where the bats are flying out of your house and how many of them there are. Use a notepad sketch of your house and mark the spots that you observe the bats exiting your home. The exact type of bats is important to perform a proper exclusion, because of their different sizes, behaviors and birthing seasons.

Bat Maternity Season

You do not want to attempt to get rid of bats during a maternity season because it will most likely end up a disaster. It’s inhumane and illegal to trap baby bats inside preventing the mothers from being able to take care of their young. Your problems will be worse because the babies cannot fly and will crawl around your walls or end up inside your home, in search of food. Most female bats will give birth in the spring, and babies will be able to fly around the end of August, so do not try to remove bats between April and August.