Bats are important indicators of a healthy environment. Because they are sensitive to high pollution and pesticide levels, they are useful as a warning sign to potential environmental problems. Also, bats can be important weapons in combating insects that are actually dangerous to humans. A small bat can capture more than 1,200 mosquitoes in a single hour! Also, bats cannot contract the West Nile Virus by eating infected mosquitoes. Besides mosquitoes, bats can help control the populations of beetles, moths, and leafhoppers. Many insects can hear bats up to 100 feet away and will avoid those areas occupied by bats. The effectiveness of bats in some areas diminishes the need for pesticides that can harm both the pests and their natural predators.
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, and are the most frequent users of bat houses. Other species that may be in your area include the Pallid Bat and the Brazilian (Mexican) Free-Tailed Bat. You can often find out what other types of bats reside in your area by calling your local park service.
Putting up a 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 their homes. Many people inquire about purchasing bats for their bat house. Bats are a protected species and are considered public domain, which means that it is illegal to own, sell, or purchase bats.
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 this is generally discouraged because of the risk of exposure to harmful bacteria than can exist in the guano.
You should always consider design when selecting your bat house. According to research, larger bat houses (often called nursery houses) have higher occupancy rates than the smaller houses. We often recommend a minimum capacity of 100-300 bats. Multiple bat houses will often increase occupancy rates. By combining a larger house for the females and their pups and a smaller house for the more solitary males, people are able to establish larger and more stable bat colonies. In addition to size, there are other factors to consider. All landing areas and partition surfaces should be rough to allow bats to easily cling when landing and roosting. Ventilation gaps are important where average July temperatures exceed 85 degrees Fahrenheit.
You may place your bat house on a tree, pole, or a building; however, boxes mounted on poles or buildings tend to have a higher occupancy than those mounted on trees. For mounting on buildings, wood or stone buildings are best, and your bat house should be mounted under the eaves with 6-10 hours of sun exposure depending on your region. You should mount your house 15-20 feet above the ground where it will not be exposed to bright lights. Also, you should place your bat house where it will receive at least six hours of sun if you live in a region where average July temperatures range from 80 to100 degrees Fahrenheit. If you live in a region where average July temperature are less than 80 degrees Fahrenheit, you should mount your bat house where it will receive at least 10 hours of sun.
While it is not necessary to paint a bat house, doing so can often help in regulating the temperature inside the house. Bat houses in warmer areas, such as the southern United States, may benefit from light colored paint. Cooler areas, such as the northern U. S. and Canada, may benefit from a darker color to help absorb more warmth from the sun. Do not paint inside the house, as the bats need a rough natural surface to hang from when they are roosting during the day.
You may mount your box at any time of the year, but those boxes mounted in the spring are often occupied more quickly. If you are evicting a colony of bats from a building, a box should be mounted several weeks prior to the eviction.
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.
Bat houses are relatively maintenance free, so you should not have to clean your bat house. General maintenance, such as repainting the house, should be done when the bats have left to hibernate for the winter.
Attracting a colony can take some time, and many different factors are involved in the process. The first consideration is the location of the house. Is it up high enough? Is it close enough to water? Are there adequate food sources nearby? The second consideration is temperature inside the house. If the average temperature is too hot or too cold or is inconsistent, bat colonies may not stay. By limiting or increasing the amount of sunlight a house receives in order to maintain a consistent warm temperature. Other factors that affect bat house occupation include the use of pesticides nearby, human activity, and lack of vegetation.
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 close by where the bats will become accustomed to it.
Approximately 70 percent of all bats are insectivores, including the majority of North American bats. North American bats primarily feed on night flying insects, especially mosquitoes, and are known to eat beetles, moths, and leafhoppers.
It is important for people to remember that bats are wild animals and should be allowed to live in their natural environments. Bats are not aggressive animals and do not intentionally attack people or other animals, however, they will bite if touched. 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.
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 protective covering. If possible, it is recommended to have a pest removal specialist remove the potentially infected bat.
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. Bats in warmer climates, such as the southern United States, do not hibernate. Instead, they go into a state of torpor if outside temperatures approach 32 degrees Fahrenheit. 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.
We now offer the Bat Builder's Handboook by Merlin D. Tuttle and Donna L. Hensley that includes bat house plans as well as general information about bats. In addition, you may find plans online at: