Bats

Attracting bats to your yard is becoming a new alternative to insect control. Bats are the only major predators of night-flying insects. These nocturnal flying mammals can eat 3000-7000 insects each night and can be an important weapon in a chemical-free arsenal for bug control. There are 15 species of bats known in Virginia and many use bat houses.

Careful consideration of bat needs may increase the chances of successfully attracting them. Bat houses located near a permanent source of water, especially a marsh, lake or river, are more likely to attract bats. Houses placed more than a half-mile from water have a lower chance of being used. Place houses 10-15 feet high, facing southeast or east, and sheltered as much as possible from the wind.

Internal temperatures may control how and whether your bat house is used. You should consider several factors before mounting a house. Bat houses intended for use by nursery colonies should be oriented to receive maximum solar radiation, especially in the morning. Painting your bat house a dark color will make it warmer. If your bat house is too cool for a nursery colony, you may still attract bachelors.

Female bats normally prefer stable temperatures of 80-90 degrees F, although some bats tolerate temperatures in excess of 120 degrees F. Bats reproduce slowly (usually only one pup annually), but sometimes form large colonies. Bat colonies are easily destroyed, causing local extirpation in some cases. Male bats do not live with females while young are being reared.

Your bat house may or may not be used during the first year. If your bat house is not occupied by the second year, try moving it to a warmer or cooler location. Chances of early occupancy are probably increased if houses are hung by early April. Occupancy rates are also increased if bats already live in barns or attics nearby. In some areas, heavy use of pesticides, a lack of hibernating sites, too great a distance to feeding or drinking sites, or even an abundance of existing roost sites may preclude occupation of your bat house.

Many commercially available bat houses are designed or constructed poorly. They often are too small and do not have a landing plate. Houses should be made of quality, untreated, rough-cut lumber or have all inner surfaces and entrances slightly roughened, scored, or covered with plastic mesh (metal mesh may harm bats). Rough surfaces allow bats to move around or attach themselves to the surface. Roosting chambers should be at least 20" tall, and roost partitions should be spaced about ¾" apart. Ventilation vents are required. Inspect your bat houses regularly, making sure to check for unintended cracks and removing wasp or bird nests during November - February when bats are away.

Last modified: Monday, 10-Mar-2008 19:46:32 UTC