Frequently Asked Questions
Merely putting up a bat house will not lure a bat colony out of a house. Successfully evicting a bat colony requires a few steps. The first step is to inspect the inside of the house for small openings through which bats could enter. All openings connecting the attic or other roosting areas to inside living areas should be sealed, although entry places on the outside of the house should be left open, allowing bats to exit. At dusk, watch the bats leaving the house to locate exactly where openings are located. Be sure to scout all sides of the house as there is often more than one opening. Entry places should be covered with a plastic mesh or netting that will allow the bats to exit by crawling under the mesh, but not re-enter the house. You should not evict bats during the months of June, July, or August, because there could be many younger bats that have not developed their flight abilities and are dependent on their mothers for food. Also, remember that you will want to put up a bat house nearby several weeks before the planned eviction. It is best to put the bat house in a place nearby where the bats will become accustomed to it. Click here for detailed instructions on bat eviction.
If there’s a bat in your house …
Don’t panic. The solutions are simple.
Bats are rarely aggressive, even if they’re being chased, but they may bite in self-defense if handled. As with any wild animal, bats should never be touched with bare hands. Always wear gloves when removing bats. Only a small percentage of bats (about one-half of one percent overall) have rabies, but anyone bitten by a bat should immediately seek medical consultation.
A solitary bat – often a lost youngster – will occasionally fly into a home, garage or other building through an open door or window. When this happens, the bat’s primary goal is to escape safely back outside. As long as no direct human contact with the bat has occurred, it can be released outdoors.
These bats will usually leave on their own if a window or door to the outside is opened, while interior entrances are closed.
If the bat does not leave on its own, it can be safely captured and released outside. (See the illustrations). Wait until the bat lands, then cover it with a small box or other container. Slip a piece of cardboard between the wall and the container, gently trapping the bat inside. Wait until nightfall and, with the bat inside the cardboard-covered container, take it outdoors and release it.
Most bats, however, cannot take flight from the ground. The bat can be released by holding the container aloft, lifting the lid and gently tilting the container to the side. The bat should fly out and away. Or you can hold the container against a high wall or the branch of a tree and slowly remove the cardboard. After a few moments, the bat should cling to the surface and can be left there.
If the bat appears unable to fly and falls to the ground, it may be injured or sick. In that case, gently return it to the box, cover it and call a local wildlife rehabilitator (here are two sources of rehabilitators, courtesy of batworld.org and basicallybats.org) or your local animal control or public health office.
If bats move in
As bats lose their natural roosts in trees and caves, they are sometimes forced to seek shelter in human-made structures. There is little reason to evict these highly beneficial animals unless they are causing a problem or are considered a nuisance. Bats should, however, be prevented from entering human living quarters.
Permanently – and humanely – evicting bats from buildings is not particularly difficult, but it requires patience and attention to detail. You can do it yourself with the following detailed instructions. Or you may prefer to contact a BCI-approved bat-exclusion professional. You’ll find BCI’s state-by-state listing of professionals who pledge to use safe and effective exclusion methods here.
Where bats roost in buildings
Bats may roost in attics, soffits, louvers, chimneys and porches; under siding, eaves, roof tiles or shingles; and behind shutters (see diagram). In stadiums and parking garages, bats sometimes roost in expansion joints between concrete beams.
Lone Star Woodcraft bat houses require very little maintenance, and do not require cleaning. General maintenance, such as removal of any wasp nests, or restaining/repainting, should be done when the bats have left for the winter. Over time, your bat house may require re-caulking to exterior joints to ensure adequate heat retention and weatherproofing.
One easy way to find out whether or not your bat house is occupied is to look for bat guano (bat droppings) under or near the bat house. Another way is to shine a strong flashlight up into the house. It is recommended that you only do this once a week, as frequently disturbing a colony can cause them to abandon the bat house.
In most of North America, bats hibernate from late fall until early spring. They often seek out caves and abandoned mines, and will migrate from their current homes (buildings, bat houses, etc.) to warmer, more secure places. Some species, such as the Mexican Free-Tailed Bat, migrate in the winter to warmer climates such as Mexico.
Some bats in warmer climates do not hibernate. Instead, they go into a state of torpor, or temporary hibernation, if outside temperatures approach 32°F. Torpor is a state of inactivity in which the bats stay in their day roosts for extended periods of time to conserve energy until temperatures begin to rise.
Many people think that by spreading bat guano on or near their bat house, it will attract a bat colony. This has not been scientifically proven, and is generally discouraged because of the risk of exposure to harmful bacteria that can exist in the guano.
Putting up a certified bat house is the first step toward attracting bats. Suitable housing for bats is rapidly decreasing in many areas, as many people view them as pests and try to evict them from buildings. Attracting a colony can take some time. Some factors to consider include bat house location/height, bat house temperature, and a water source nearby. Click here to learn more about where to mount your bat house.
Bats are found on every continent except for Antarctica. They are particularly abundant in North America, and many people in the United States and Canada have bats in their backyard without even knowing it.
Most areas have several different species of bats. The Big Brown Bat and the Little Brown Bat are the most abundant bats in the United States. Other species that may be in your area include the Pallid Bat and the Mexican Free-Tailed Bat. You can find out what types of bats reside in your area by sending us an email.
Many people have serious misconceptions about bats. Perhaps one of the most popular of which is the belief that bats are vicious carriers of rabies. The fact is that bats are actually quite harmless, and do not exhibit any higher percentage of rabies infection than any other animal species. In fact, bats infected with rabies usually do not exhibit the aggressive behavior that often occurs with rabies infection in other animals. Rabies infection normally paralyzes the bat, so do not pick up a bat that may be lying on the ground without thick protective gloves. If in doubt, contact your local wildlife control agency.
It is important for people to remember that bats are wild animals. Bats are not aggressive, and do not intentionally attack people or other animals. However, they will bite in self-defense if handled. Caution is always recommended when finding a dead or injured bat.
Birding enthusiasts should not worry about competition between bats and birds. Since bats are nocturnal, they rarely come in contact with most birds. Also, there is rarely competition for food since there is not typically a shortage of insects that are consumed by both bats and insect eating birds, such as the purple martin.
Bats are valuable allies, well worth protecting. Worldwide, they are primary predators of vast numbers of insect pests that cost farmers and foresters billions of dollars annually and spread human disease. For example, in the United States, Little Brown Bats often eat mosquitoes and can catch up to 1,200 tiny insects in an hour. An average-sized colony of Big Brown Bats can eat enough cucumber beetles to protect farmers from tens of millions of the beetle's rootworm larva each summer. Large colonies of Mexican Free-Tailed Bats eat hundreds of tons of moth pests weekly. Bats play key roles in keeping a wide variety of insect populations in balance. Yet, they rank as North America's most rapidly declining and endangered land mammals. The largest known cause of decline is exaggerated human fear and persecution.
General speaking, bats are important indicators of a healthy environment. Because bats are sensitive to high pollution and pesticide levels, they are useful as a warning sign to potential environmental problems. Further, the effectiveness of bats in some areas diminishes the need for pesticides that can harm both the pests and their natural predators. Some species of bats are also vital pollinators of many plants.
Bats are also important weapons in combating insects that are dangerous to humans. With the increased media coverage of the dangers of West Nile Virus, many people are looking for effective ways to prevent the spread of the disease. As most of us are aware, West Nile Virus is primarily spread through mosquitoes. Mosquitoes make up a significant portion of a bat’s diet, and bats cannot contract WNV by eating infected mosquitoes. Approximately 70% of all bats are insectivores, including the majority of North American bats. North American bats primarily feed on night flying insects, especially mosquitoes. A small bat can capture more than 1,200 mosquitoes in a single hour! One of the most effective and environmentally friendly ways to reduce the mosquito population near your home is to install a bat house.
Besides mosquitoes, bats can help control the populations of beetles, moths, and leafhoppers. Bats that live in our yards, in addition to eating pests, serve as natural insect repellents. Many yard pests, especially moths that attack gardens, lawns, and shrubs, can hear bats from over 100 feet away and attempt to avoid them by leaving the area!
You can mount your bat house at any time of the year. If you are evicting a colony of bats from a building, a bat house should be mounted several weeks prior to the eviction.
While in many cases it is not necessary to paint or stain a Lone Star Woodcraft bat house, doing so can sometimes help to maintain optimal temperatures in cooler/northern climates. Cooler areas, such as the northern U. S. and Canada, may benefit from a darker color to help absorb more warmth from the sun. Never paint or stain inside the bat house or the landing pad, as the bats need a rough natural surface to hang from when they are roosting or landing, and this may be compromised by paint or stain. Also, keep in mind that cedar will naturally darken in color over time. See our Region Map for staining/painting recommendations.
Depending on the climate where you live, you should place your bat house as follows:
•If your average July temperatures are greater than 80°F, mount your bat house where it will receive at least 6 hours of sun.
•If your average July temperatures are less than 80°F, mount your bat house where it will receive at least 10 hours of sun.
You may place your bat house on a pole, building or a dead or unbranched portion of a tree. Bat houses mounted on poles or buildings, however, tend to have a higher occupancy than those mounted on trees. When mounting on buildings, wood or stone buildings are best, and your bat house should be mounted under the eaves with sun exposure. You should mount your house 15-20 feet above the ground. Avoid areas that are brightly lit at night. Placing your bat house near a water source such as a stream, river, lake, pool or even birdbath can exponentially increase your chances of attracting and keeping bats. For more information on mounting options, visit our accessories page.
Choosing a certified bat house ensures it is constructed with the best materials and to the appropriate dimensions. Lone Star Woodcraft bat houses are handmade in the USA from 100% Western Red Cedar, and certified by Bat Conservation International’s Bat Certification Program. Their program is based on many years of research to determine the most effective ways to attract bats to your bat house. Look for the logo at the top of the page to ensure you are buying a "Certified" bat house.
Certification Criteria for Bat House Design and Construction
1) Roost chambers must be a minimum of 20 inches tall. Taller is better.
2) The width (side to side) of roost chambers must be at least 14 inches. Greater widths are preferred. Rocket style houses with continuous (360 degree) chambers are an exception. Depending on materials used, bat houses with roost chambers wider than 16 inches may require spacer blocks between partitions.
3) Roost partitions must be carefully spaced 3/4 to 1 inch apart (front to back), regardless of the number of chambers. The best crevice size for most North American bats is 3/4 inch. Houses built specifically for larger species (pallid bats and Florida bonneted bats), with a combination of 3/4- and 1-inch chambers, may be acceptable, provided houses are advertised for those species. Advertising must also state that 1 1/2-inch chambers are more attractive to wasps and other non-target animals and require more frequent monitoring.
4) Bat houses must include a suitable landing area. Either a three- to six-inch landing area must extend below the entrance (by extending the length of the backboard) or partitions must be recessed three to six inches so bats can land on the inside walls of the bottom of the bat house.
5) Interior surfaces and landing areas must have adequate texture to provide footholds for bats. Rough-cut wood may suffice or surfaces can be mechanically grooved, roughened or scored horizontally at 1/4 to 1/2-inch intervals, approximately 1/16-inch deep. Roost surfaces can also be covered with a durable plastic mesh (we recommend 1/8- or 1/4-inch square mesh. Plastic mesh must be securely stapled every two inches (up, down and across) so it does not sag, buckle or curl. Mesh must not have sharp edges (trimming may be necessary). Metal mesh, hardware cloth or aluminum window screen is not acceptable, as these can injure bats.
6) Screws, staples, nails, mounting hardware or other sharp objects (including splinters) must not protrude into roost chambers. All hardware and metal components must be exterior grade (coated, brass, galvanized, etc.). With few exceptions, all major components must be assembled with screws. Nails, brads or staples alone do not hold well over time. Any exposed metal edges (e.g. roofs) must be smooth.
7) Half-inch tall ventilation slots must be provided and be placed no more than one-third the distance from the bottom. Front vents must be as long as a house is wide, and side vents (optional) should be approximately six inches tall by one inch wide. Decorative vents may be allowed, provided their size and position are adequate. Unvented wooden houses are acceptable if intended for cool climates only, which must be clearly stated in enclosed literature and advertising.
8) Any plywood used must be exterior grade (e.g. ACX, T1-11, BCX). Boards should come from quality stock such as cedar or pine. Pressure- or chemically-treated wood must not be used, as they contain substances that may be harmful to bats.
9) Overall construction must reflect that the bat house is a quality product. Bat houses must be durable and tightly constructed (no unplanned gaps). Caulking or gluing exterior joints (preferably during assembly) is required to prevent drafts. If not caulked or painted by the builder, adequate instructions must be provided for customers to caulk and paint the house. Latex caulk and exterior-grade, water-based paint or stain is recommended.
10) Advertising and any instructions or literature included with bat houses must be approved by BCI. Unsubstantiated or misleading claims (e.g., "No more mosquito problems") will not be permitted. Instruction sheets included with bat houses must contain adequate information on painting, sun exposure, mounting height, mounting sites and recommended distances to water and obstacles.
You should consider design when selecting your bat house. All landing areas and interior surfaces should be rough, such as natural cedar, to allow bats to easily cling when landing and roosting. Ventilation gaps are integral to maintaining suitable bat house temperatures. According to research, larger bat houses (multi-chamber or "nursery" houses) have higher occupancy rates than single chamber houses. Most North American bats prefer to live in large groups, called colonies, so a house that can hold at least 300 bats is typically recommended. An alternative approach is to combine a larger house for the females and their pups, and a smaller house for the more solitary males, which can establish larger and more stable bat colonies.