Bats are flying mammals that contribute significantly to the ecosystem, primarily by consuming vast quantities of insects. When these nocturnal animals take up residence inside human structures, they can pose a public health concern and cause damage. Preventing bats from entering your home and knowing how to handle encounters is essential for safety.
Sealing Structures to Prevent Entry
The most successful strategy for avoiding bats in a dwelling is physical exclusion, which involves sealing all potential entry points. Bats are able to squeeze through remarkably small openings, sometimes as narrow as 3/8 of an inch. Because they do not chew their way into a building, they rely entirely on existing structural gaps for access.
A thorough inspection of the building exterior is the first step, focusing on areas like roof edges, loose flashing, and deteriorated mortar joints. Common entry points include gaps under roof eaves, ridge vents, gable vents, and uncapped chimneys. Any construction gap should be scrutinized and sealed with appropriate materials like caulk, wire mesh, or weather-stripping.
If you suspect or confirm a bat roost inside, exclusion must be timed carefully and humanely to comply with wildlife protection laws. Exclusion is prohibited during the maternity season, which typically runs from May to August, to prevent trapping flightless young bats, or pups, inside the structure where they would starve. The safest and most ethical times for exclusion are in the early spring before bats return from hibernation or in the late summer and early fall once the pups are able to fly.
Once a primary entry point is identified, a one-way exclusion device must be installed to allow the bats to leave but prevent their return. These devices, which can be custom-made from netting or PVC pipe or purchased commercially, are secured over the active opening. The bats exit at dusk for their nightly foraging and cannot navigate the device to re-enter the following morning. The device should be left in place for five to seven nights to ensure the entire colony has departed before the opening is permanently sealed.
Environmental Changes to Discourage Roosting
Altering the immediate environment around a property can make it less appealing to bats. Since bats prefer dark, secluded spaces for roosting, introducing bright, continuous illumination into areas like attics or under eaves acts as a deterrent. Powerful floodlights or fluorescent bulbs installed to light up a dark roosting site may encourage the bats to relocate to a more sheltered spot.
Changing the exterior lighting around the home can reduce the local food source that draws bats to the area. Many insects, which are the primary diet for most North American bats, are attracted to standard white outdoor lights. Switching these fixtures to yellow or amber-colored bulbs decreases the concentration of insects near the home, making the location less attractive for foraging.
Repellents are generally considered less effective than physical exclusion or habitat modification. While some ultrasonic devices are marketed to deter bats, scientific evidence supporting their long-term effectiveness is limited, as bats may habituate to the sound. Naphthalene flakes, an EPA-registered chemical repellent, can be used in attics but must be applied in high concentrations and is only a temporary measure, often driving bats deeper into wall voids.
Immediate Safety Measures During a Bat Encounter
If a bat is found inside the living space, it is important to prioritize safety and never attempt to handle the animal with bare hands. Though less than one percent of bats carry rabies, they are the main source of human rabies cases in the United States. A bat bite or scratch can be so small it goes unnoticed. Direct contact with a bat should be avoided at all times.
If a bat is discovered in a room with a sleeping person, an unattended child, or an incapacitated individual, immediate medical attention is necessary, even if there is no visible bite mark. In these scenarios, the possibility of an undetected exposure to the rabies virus is high, and post-exposure prophylaxis (PEP) is typically recommended. If you are certain no contact occurred, confine the bat to one room, open a window or exterior door, and allow it to leave on its own.
If contact is suspected, the bat must be safely captured for rabies testing, not released. Wearing thick leather gloves, a person can wait for the bat to land, cover it with a coffee can or small box, and slide a piece of cardboard underneath to trap it. Contact the local public health department or animal control immediately to coordinate the bat’s submission for testing, which determines if PEP treatment is required.