Bats are a beneficial and interesting mammal. They are the single most important controller of night-flying insects, including mosquitoes, moths, and beetles. Of course, watching them skillfully fly around your yard can also be great fun. This article will explain bat behavior and teach you how to construct a bat house of your own.
Learn about the bats of your region. There are two broad types of bats, and each have different appearances and characteristic.
The bats that inhabit the temperate regions of Europe and North America all fall within the family Microchiroptera (roughly, “small bats”). Other than their small size (which is more of a common trait rather than a defining characteristic), they are physically unique from their cousins in that they tend to have short noses or muzzles, smallish eyes, and larger ears.
Megachiroptera is the suborder that represents most of the larger bat species of the world, but they are generally restricted to the tropical environments that stretch from Australia to South Asia and on to the Mediterranean. The species which make up this group tend to have longer muzzles and, some would say, even a vaguely rat-like or canine appearance. Because of this, several species native to Australia and Southeast Asia are commonly referred to as “flying foxes.”
Understand the feeding habits of bats. If you want to attract bats to your home, the likeliest way is to guarantee a ready supply of food.
The small bats that occupy much of the temperate regions fly at night and use echolocation to find the flying insects that make up most of their diet. If you do not have insects outside of your home at night, you may not be able to attract bats.
Larger tropical bats live primarily on a diet of fruit and nectar. They may search widely over the course of a year looking for ripening fruits or flowering plants.
Determine the type of place where local bats rest. While food is the dominant factor in the ability of bats to thrive in an environment, they do also require shelter. This, too, differs by type.
Small insect-eating species tend to live in caves or in the hollow of a tree. Many species crowd very closely together, which can help them retain heat. Because they like to stay in enclosed spaces, many of them can be enticed to live in specially constructed bat houses.
The flying foxes and other larger fruit bats usually roost in very dense concentrations in a relatively small section of forest. Because of the sounds, smells, and overall destruction that can come from hosting a horde of several thousand of the bats, in most areas their roosts are considered a nuisance to be removed.
Think about how you can use bat behavior to your advantage. If your goal is in fact to attract bats to your yard, you should consider how the needs of the animals fit with the environment you have created. Ask yourself these questions:
Are there places for the bats to stay or rest? If not, you will not have bats that live on your property.
Are there potential food sources? The most common bats to visit backyards are usually insect eaters. If there are no insects due to the use of pesticides, you will not likely have bats.
Are there their irritants that may discourage bats from coming to your yard? For example, many of the insect-eating bats use a combination of echolocation and passive listening to determine the location of the insects they prey upon. If you are in a loud neighborhood, those species would not be effective hunters and would stay away.
Find an appropriate location. A bat house does not need to be large, but when considering a potential location there are a few points you should keep in mind.
The house should be placed at a point roughly 15 feet off of the ground and inaccessible to climbing predators.
The house should be placed in a location that receives sunlight for most of the day.
Understand how a bat house should look. In nearly all ways that it can, a bat house will differ from the bird houses with which most people are so familiar. Here is a list of the basic characteristics:
Unlike birdhouses, the opening for entrance and exit will not be at the front. Instead, there should be a long open strip along the bottom. The entrance and the back wall of the bat house should be covered in a kind of mesh that the bats can climb with their their claws.
It should not be cube shaped (as is common for many bird houses) but instead be a very wide, fairly tall, flat box. Keep in mind that you are not making this house for a single bat or even a pair of bats. Many bats rarely settle down for the day in groups of less than a dozen. According to those who have customized bat houses based upon studies of behavior, the smallest bat house should have exterior dimensions of roughly 13 1/2 inches wide, 3 3/4 inches deep, and 20 inches tall (with an additional 4 or 5 inches of the back wall extending below the floor to the entrance, providing something for the bats to latch on to).
There should be several narrow open strips along the lower portions of the sides to to vent air from the box. Because they often rest in densely packed groups, the heat they generate and CO2 they release can make a bat house unlivable very quickly.
Identify and obtain needed materials. These are the primary tools you will need:
A pole (optional) on which you will mount the house when completed.
Lumber, including 3/4 inch plywood and that has been treated to make it water resistant.
Cut the lumber. The largest piece should be used as a back wall for the bat house. It is a good idea to cut out notches in the front and sides to serve as ventilation slits before you finish assembling the bat house.
All ventilation slits should be made no larger than 1/4 of an inch. If the slits are slightly greater than that, they could allow too much cold air in. If the slits are 1/2 an inch in size or more, it would allow small birds to take over the house as a nesting area for themselves and exclude bats altogether.
The roof should be long enough to extend from a position above the back wall to a place several inches beyond the front wall. It can be installed to meed the back and front walls at a 90 degree angle, but if you want to roof to be at a 30 degree angle it will have to longer. You may also want to cut the roof, front wall, and back wall to an angled edge on one side so they will fit together smoothly.
Attach the mesh to the largest of the planks. The largest plank will serve as the back of the bat house. Staple the mesh in place.
You may need to cut the mesh to fit the plank. It should be cut smaller than the width of the plank, as it should not be between the joints that connect the back to the sides and roof. However, the mesh should extend to the bottom of the plank.
Screw the floor onto the front wall. The floor should be attached to the front side only. The floor should be narrow enough that it will not touch the back wall when the house is fully assembled. The gap should be 3/4 of an inch in order to allow the bats to enter through the bottom.
Screw the front to the sides and back. Drill pilot holes using a small drill bit before you attempt to screw the pieces in place. Use a minimum of two screws per side.
Attach the roof. Again, drill pilot holes before attaching the roof. Screw the roof in place into the back and front walls. Use a minimum of two screws per side.
Paint or stain the bat house. Painting or staining the bat house will provide an additional seal and ensure that the wood will last longer.
Attach the bat house to the intended site. While you could screw directly from the bat house into the target site, it may be best to attach some kind of mounting bracket that will hold the house in place but allow you to easily move it if you so choose. If you have decided to mount it on a new pole, do so before you anchor the pole into the ground.