Bat cones are one-way exclusion devices that let bats leave a building but prevent them from getting back in. They’re the most widely recommended, and in many states the only legal, method for removing bats from a home. A simple tube or cone of mesh is placed over the bats’ entry point, angled so they can crawl or fly out the bottom but can’t navigate back through the narrow opening. Left in place for at least a week, they clear a colony without harming any animals.
How Bat Cones Work
A bat cone is essentially a funnel. The wide end attaches flush against the building over a gap or crack where bats enter and exit. The narrow end hangs open, pointing downward and away from the wall. Bats inside the structure follow their usual route toward the exit, pass through the tube, and drop into open air. When they return, the smooth, narrow opening gives them nothing to grip or squeeze back through.
Most exclusion cones are made from lightweight plastic mesh, PVC pipe, or flexible netting shaped into a tube. The key design principle is that the exit end must be narrow enough (roughly 2 inches in diameter or less for most species) and extend far enough from the wall that a returning bat can’t cling to the building surface and work its way back in. Some versions use a flap of netting instead of a rigid cone, but the one-way logic is the same.
Exclusion devices need to stay in place for a minimum of five to seven nights. Florida’s wildlife regulations require at least four consecutive warm, dry nights. Bats don’t forage when it’s cold or rainy, so if weather turns bad during that window, the clock resets. Night temperatures should stay above 50°F for the devices to work reliably, since bats may not leave the roost on colder nights. Once you’re confident every bat has exited, the cone is removed and the opening is permanently sealed the same day.
When You Can and Can’t Use Them
Timing is critical. Bats typically return to their summer roosts in late April or early May, and pups are born in late May or June. Those young bats can’t fly until mid-July at the earliest. If you install exclusion cones while flightless pups are inside, the adults leave and the pups starve, which is both illegal and creates a serious odor and contamination problem inside your walls.
The safest windows for exclusion are early spring (before bats arrive) and late summer through early fall (after pups can fly but before hibernation). Penn State Extension recommends this general calendar:
- January through April: Seal entry points before bats return for the season.
- May through July: Watch and identify entry points, but do not seal openings or install cones.
- August through October: Install one-way exclusion devices.
- November through December: Seal entrances after bats have left for winter.
States set their own restricted periods, and they vary. Ohio, for example, prohibits exclusion from May 16 through July 31 when five or more bats are present, and again from October 15 through March 31 if any bats remain. Exclusion during those windows requires written permission from the state Division of Wildlife, granted only when human health is at risk and nighttime temperatures cooperate. Ohio’s ideal exclusion periods are April 1 through May 15 and August 1 through October 15.
Legal Restrictions to Know
Every U.S. state protects bats to some degree, and several species carry federal endangered status. In Ohio alone, four bat species are state-endangered, including the Indiana bat and the northern long-eared bat. Killing a bat for any reason is illegal unless a bite or potential rabies exposure has occurred.
The only lawful removal method is exclusion. It is illegal to use glue traps, chemicals, toxicants, or foggers. Sealing all entry points while bats are still inside the structure also violates the law, since it traps and kills them. Some states require you to perform bat watches (counting bats at dusk or dawn) before you can begin, and colonies above a certain size may need a permit. If you’re unsure about local rules, your state wildlife agency will have specifics.
Steps for a Successful Exclusion
Before installing any cones, you need to find every opening bats are using. Bats can squeeze through gaps as small as 3/8 of an inch. The most reliable method is a bat watch: stand outside at dusk, starting about 30 minutes before sunset, and observe where bats emerge. Repeat this at least twice within a week. Look for dark staining or small droppings (guano) around gaps in soffits, ridge vents, fascia boards, and where different building materials meet.
Once you’ve mapped all the entry points, seal every secondary opening with caulk, mesh, or foam, leaving only the primary exit open. Install the exclusion cone over that main exit. The cone must be securely attached on all sides except the bottom, so bats funnel through it rather than around it. Leave it in place for at least a week of favorable weather. After the last bat has exited, remove the cone and seal the final opening on the same day.
If you find more than one or two bats in your living space, or if entry points aren’t obvious, hiring a wildlife damage control professional is worth the cost. Improper installation is the most common reason exclusions fail, and a missed gap means the colony simply shifts to a new entry point.
Rabies and Safety Precautions
Bats are the most common source of rabies exposure in the United States, and the risk doesn’t require an obvious bite. Any direct physical contact with a bat counts as a potential exposure when a bite or scratch can’t be ruled out. The same applies if a bat is found in a room with a sleeping person, an unattended child, or anyone who may not have been alert enough to notice contact.
If anyone in your household has been potentially exposed, the bat should be captured safely (wearing thick leather gloves, never bare hands) and submitted for rabies testing. When the bat isn’t available for testing, post-exposure treatment is typically recommended. Handle the health concern first, then address the exclusion.
During the exclusion process itself, avoid direct contact with bats or accumulated guano. Bat droppings can harbor fungal spores that cause a lung infection called histoplasmosis when inhaled. If your attic has a significant guano buildup, cleaning it out safely may require respiratory protection and professional help.
Why Bats Are Worth Excluding, Not Killing
A single bat eats thousands of insects per night, including mosquitoes and agricultural pests. Colonies provide enormous pest control value, which is why laws protect them so strictly. The goal of exclusion isn’t to eliminate bats from your property. It’s to move them out of your walls and into the trees, bat houses, or other natural roosts where they belong. Many wildlife agencies recommend installing a bat house nearby before starting an exclusion, giving the displaced colony an immediate alternative.
Bat cones installed at the right time of year, left in place long enough, and followed by thorough sealing resolve the problem permanently for most homeowners. The bats survive, relocate, and continue doing what they do best somewhere that isn’t your attic.