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A Boxful of Bats

What's flat and black and sits atop a pole going "squeak, squeak, squeak"? A bat house, of course.

All across the country, people are putting up these curious structures to provide local bats with places to rest and, in some cases, raise young. And for good reason: with more than 50 percent of American bat species in severe decline or already listed as endangered, these creatures need our help.

In the past bats used tree cavities and other natural features for shelter. As towns and cities expand, fewer of these natural sites remain, and bats are forced to occupy places like attics and wall spaces. Some of the people who need to exclude bats from roosting in their homes erect bat houses to offer a housing alternative to the colony being evicted.

Other people erect bat houses in an effort to reduce the number of bothersome insects in their area. And while it's true that a single Little Brown Bat -- one of the most common species in the country -- can eat 1,200 mosquito-sized insects in an hour, it's unlikely that an isolated bat house will affect the overall insect population. The same probably applies to the large bat houses that farmers build to control insect pests. Still, every pest eaten helps.

Another reason people construct bat houses is for the fun of it. There's a thrill that comes with peering into a box one day and seeing a group of tiny furred creatures resting inside. Most parts of the United States feature eight to ten species of bats, and sometimes more, but people seldom notice them. Erecting a bat house and watching it become occupied is a great way to confirm their presence.

A successful bat house involves two elements: proper design and proper placement. The bats that use bat houses are those that roost in crevices. Therefore the size and shape of the opening and the configuration of the interior are crucial. Temperature and ventilation are also important, which means that the exposure and the color (which influences the heat absorption) must be considered carefully.

For information on building the perfect bat house and setting it up right, visit the Web site of the North American Bat House Research Project. It's even possible to download construction plans from the site. Just remember that bat houses require patience. If one doesn't attract tenants the first year, the odds of occupancy increase during the second year.