Bat Houses

If you would like to retain a family of bats for their excellent insect control abilities, why not consider building or installing a bat house? Bat houses, much like bird houses, provide artificial roost sites for bats. They have been widely used in Europe for over 60 years. Much has been learned in recent years about bat roosting preferences. The following factors are critical to the success of bat houses: maintaining suitable temperature ranges, the distance to food and water, the size and shape of inner roosting spaces and the roughness of clinging surfaces.

Bat house designs range from simple and small-scale to large and complex. If you're interested, The Bat House Builder's Handbook is packed full of plans and information. The small bat house (see the how-to) provides only one size roosting space and accommodates fewer bats. The large bat house (see the how-to) provides many roosting options and is ideal for larger nursery colonies of females and young.

Below are tips for constructing and installing a bat house:

1. Use the roughest sides of the wood on the inner areas of the house. It is also a good idea to horizontally groove inner surfaces for footholds or attach non-metal screening to provide toe holds. This is also important for landing areas below the entrance.
2. Caulk all outside seams to limit air flow. This helps trap the bats’ body heat inside the house. Sealants approved for aquarium or kitchen use are best.
3. Place tar paper or dark shingles on the top and 4 to 6 inches down the side to increase inside temperatures. Nursery roosts often require temperatures of 90 degrees F or more.
4. A dark stain also helps increase the temperature.
5. Hang houses 10 to 15 feet above ground. South and southeast exposures are best for providing maximum thermal gain. Bats prefer houses that get at least 6 hours of sunlight a day.
6. If possible, protect the house from prevailing winds and provide an unobstructed approach.
7. Bat houses attached to the sides of buildings have had the greatest reported success. Free-standing poles in open areas also work, but tree-mounted houses generally remain unused.
8. Bat houses placed near water or wetland areas often are most successful. Installing a bat house before April improves the chance of occupancy. Don’t be discouraged if bats do not immediately move into their new home. It is not unusual for a house to stand empty for at least a year before it is used.

source: DEP