Bat Exclusion Process - Step-By-Step

1) First, you've already done the bat inspection process to determine where all the possible entry holes into the building are located. You've identified the primary entry and exit areas. You've already sealed shut the holes and gaps that the bats aren't actively using, but COULD potentially use to get back in once blocked out. You've followed my bat repairs process to use proper materials.

2) Second, you've identified the species of bat during your bat inspection process, by observing them in the attic, by watching them fly out of the house at dusk, and by examining the bat poop that you see in the attic or the ground below the entry holes. You've researched when they have their young (summer for all species), so that you don't do your exclusion during the bat maternity season.

3) Okay third, now you have to set the proper exclusion device on the bat exit gaps and holes. Here is the general principle: the device has to be set on the exit hole/gap in such a way that the bats are able to naturally exit the building as they always do. They have to crawl out and fly out or flutter down through the device. They won't exit the building if there's an obstruction in the way. In addition, the device must be configured so that the bats are not able to fly back in when they attempt to return. It all has to do with the way bats take off and land. It's tricky to describe, and this is one of the reasons experience really helps in a successful exclusion. I've seen hundreds of cases now, and made many small adjustments.



Exclusion Devices
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 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 horizonal or tricky architecture, when the bats are leaving out of a small hole.

Batcones - these are special funnels with a tapered body and attachment wings that you can purchase online.

TIP: Do at least one dusk bat observation to determine the most popular points of entry and exit. This will tell you where to set the exclusion devices.

TIP: I often set these exclusion devices at night, when a good % of the bats are already out. I've found that with a large colony, if a few of the initial scout team doesn't leave because they are wary of the exclusion device, that results in a backup. If you do it at night, many of the bats have left when things were clear and easy, and then the exclusion devices clear out the remaining bats inside.



4) Leave the exclusion devices up for at least three days to be sure. Monitor each night, and if you can get up, at dawn, to see how the bats are reacting. If you still hear bat chirping inside or any other sign after the second day, you've done something wrong! Remove the exclusion devices immediately and start over.

5) After you are sure all the bats are out, remove the exclusion devices and seal the final holes/gaps shut.

TIP: I often do the seal-up work at night! Yes, I'm high on a ladder and crawling all over a roof at night. Why? Because it's so much easier to spot all the gaps and crack at night while focusing a high-beam headlamp on the building. You might think this is silly or counter-intuitive, but again, I've done hundreds of bat jobs, and I've learned that the work is more effective this way. You'd be amazed at the holes you see at night that escape you by day, and the bat behaviors you see that ensure 100% success. Remember, it's not like I prefer to be working in the middle of the night! It's just that it helps get the job done perfectly, and perfection is required.

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Wildlife Education - Information and Advice for the Safe Removal of Bats from Attics