Six Tips on Selecting and Locating a Bat House

Recently, I got a great deal on a bat house with a coupon for $25 off any purchase from Gardens Alive. Excited at the prospect of having my own bat colony and fewer bugs in my yard, I did a bit of research to learn how to make it more attractive to bats. Here are six things I learned, including some I wish I'd known before I chose my bat house.

One: Bats are Choosy
Not all bat houses attract bats. The odds of attracting bats to well-designed, well-built bat houses are pretty good, says Bat Conservation International. According to Bat Conservation International's 1999 to 2001 annual surveys, occupancy rates averaged 60% for all reported bat houses: 61% in rural areas and 50% in urban and suburban areas. Tall multi-chambered designs and rocket-style houses had the highest occupancy rates.

The organization found that 90% of occupied bat houses were used within 2 years, with 50% occupancy in the first year. They recommended relocating a bat house that had remained unoccupied for two or more years.

Two: Design Matters
Bat Conservation International recommends that bat houses be at least 2 feet tall and have chambers at least 20 inches tall and 14 inches wide. A landing area should extend at least 3 to 6 inches below the entrance; grooved or rough surfaces in this area help the bats land. Taller and wider houses are even better. Rocket boxes must be at least 3 feet tall and have at least 12 inches of linear roosting space. A box with several small roosting areas, and roughened surfaces, is more likely to attract bats.

Three: Placement Matters Too
Bat Conservation International found that occupancy rates for bat houses varied considerably, depending on where and how they were mounted. Bat houses on the sides of buildings were occupied 64% of the time, but only 30% of the time when mounted on poles. They were most likely to be occupied when mounted 15 to 18 feet above the ground. Only 5% of those mounted lower (10-12 feet) were occupied.

Four: Bats Like it Warm
According to Bat Conservation International, the most important factor in determining whether a bat house will be successful is the interior temperature, which should be as warm and stable as possible. Bats raising their young typically prefer temperatures ranging from 80 degrees to 100 degrees F. Factors that affect the internal temperature include the exterior color and the orientation of the house. Generally, seven or more hours of direct sunlight is recommended, more in areas where daytime temperatures usually stay below 80 degrees F.

Five: Avoid Common Mistakes
Writes Bat Conservation and Management Inc., "The greatest bat house in the world will never contain a bat unless it is placed properly in the field." Too much shade, mounting on a tree or on a structure under the eaves of the roof, or too far away from permanent water may all prevent the box from being occupied. In placing the box, avoid mounting it where dusk-to-dawn lights shine directly onto it. Because bats drop guano, avoid placing the bat house above windows, doors, decks, or walkways.

Six: Maintenance is Important
Once you've attracted the bats, you must maintain the house to keep them coming back. To do this, remove wasp or other insect nests each winter after the bats and wasps have left. You may need to recaulk the bat house and apply new paint or stain every three to five years to guard against leaks and drafts. Check the house at least once a month for potential problems, such as predators, overheating, or deterioration of the wood. Do any repairs or cleaning when the bats are not there.