Tips to make sure bats stay outside house

Few things are as startling as waking up in the night with a bat winging over the bed. These superb flying mammals normally cruise the sky snatching insects from the air, but once in a while one ends up inside. Deadly white-nose syndrome has plummeted bat populations across much of the Eastern United States. That's great news for mosquitoes. Fortunately bats still are relatively common in Iowa where nine species are native. Big and little brown bats remain abundant. The name is misleading since even big brown bats weigh barely an ounce and can squeeze through a crack only 3/8 of an inch wide.

Bats are nocturnal and normally spend days roosting in large hollow trees. Dark, warm attics, especially in older frame homes, make acceptable substitutes, and sometimes hundreds of bats live upstairs without human occupants realizing it.

Most people appreciate bats for their amazing ability to eat pesky insects, but hardly anyone wants one in their home. Many people have a deep almost paralyzing fear of bats that may stem from rumors of the animals tangling themselves in human hair. That doesn't happen. Bats can carry rabies but the odds of it being transmitted to a person are tiny.

If a bat is discovered flapping around inside the house it might be just a single one that somehow entered and is trying to leave. To encourage eviction, open doors and screenless windows and turn on lights. Bats prefer darkness and usually exit quickly.

Any bat inside a home is a sure sign that there is a crack or hole in an exterior wall or a gap around windows or doors. Caulking and weather stripping is a near foolproof way of keeping both bats and cold air from entering, an important and inexpensive home maintenance project.

Sometimes people unknowingly share their home with a bat colony living in a rarely visited corner of the attic. Colonies might only summer upstairs but big brown bats hibernate in homes and can be heard scratching around during January thaws.

One way to tell whether bats have moved in is to check the attic in the middle of the day armed with a flashlight. Look for them hanging from the ceiling and droppings, called guano, on the floor.

A more pleasant way is to circle outside the house with a pair of binoculars seeking holes and cracks in the siding and around windows and soffits. Bats often come and go from the same crack and eventually leave a dark stain on the paint that reveals their doorway. Watching the house at twilight also can pinpoint where they get in and out.

If a colony is living upstairs, call a bat control specialist. Professionals often use a one-way device over the crack that allows bats to leave unharmed but prevents re-entry. Once the entire colony has vacated, they will caulk entry points to keep them out.

Erecting bat houses sometimes will keep a colony in the yard while caulking prevents them from coming inside your home.

' Marion Patterson is a retired educator. Richard Patterson is the former executive director of Indian Creek Nature Center in Cedar Rapids.