Bats - A Scary Surprise

Mary Ann Ryan
Adams County Master Gardener

With Halloween just around the corner, witches, scarecrows, ugly monsters and bats are often on the kids' minds. But are bats really as scary as witches and monsters? I don't think so. There is some real value to having a bat colony near you, and not just at Halloween for the "fear factor".

What do you know about bats? Chances are what you think you might know, probably isn't true. Bats are not blind, nor are they rodents or birds. They are not going to "suck your blood". The reality of it is that many bats can see very well. They are mammals, like you and I. Most eat insects, except for the vampire bat, not found in our area. They depend greatly on sound and very good hearing to find food and to get around in the dark.

As a matter of fact, we greatly benefit from the bat population. Bats eat insects, including mosquitoes. One little brown bat can catch 1200 insects in an hour. A nursing mother bat eats more than her own body weight nightly - up to 4500 insects! This helps to control our insect population. They reseed cut forests. Bats pollinate flowers for us, which then provides us with food.

There are nine species of bats that live in the northeastern United States at least part of the year. The little brown bat and the big brown bat are the most common in Pennsylvania, but you may also see silver-haired, red and hoary forest-dwelling bats as well. Bats survive both the highest and the lowest temperatures of any American mammal. Hibernating red bats can survive temperatures as low as 23 degrees F., and little brown bats can rear young at 122 degrees F. Little brown bats can live up to 34 years, bur they reproduce slowly. Most species bear and nurse only on pup a year.

Now that you know that bats are beneficial, how can you attract them? Understanding where bats live is the first step. In the summer, many find trees to roost and raise their young. They will hide beneath tree bark, in tree crevices, and under the foliage. They live in caves, mines and caverns. Abandoned houses, buildings, and bridges can be a likely place to find bats. In the winter, some migrate south, while others hibernate in the caves and mines, and sometimes in buildings. Bat houses are a common way to attract bats to your yard. These are available on the retail market today, and if you're handy, you surely can find plans to build your own.

Bat houses can occupy from 50 to 200 or more bats, depending upon the chambers within the bat house. The bats will colonize wherever there is food. Near water would be a great location to place a bat house. The box should face southeast or southwest, so that they receive at least seven hours of direct sunlight per day during the spring and summer. The box should have at least 3 feet underneath it so the bats can enter and exit from the bottom.

Okay, so you're convinced that bats are beneficial, you may even want to build a bat box to start a colony near your home, but you don't want those bats in your house, or you may even have a bat or two in your attic now. What should you do to get rid of these beneficial mammals without hurting them or to keep them from entering your home? There are three steps to bat-proof your home. First, identify bat entrances. Locate the holes that bats may use to enter and exit the attic. Bats often enter at points where joined materials have warped, shrunk or pulled away from one another. Second, seal the holes to prevent their entry; and third, provide and alternative roost for the colony to occupy.

Timing of bat proofing is very important. Pups remain confined in the roost until they are old enough to fly, therefore, bat proofing should not be completed in May through July. Otherwise, the bat pups could be trapped inside the building. The best time for bat proofing is in January through April, before bats enter the roost, or in the fall, after the bats have left.

Here is the time line to exclude bats from your attic: "January through April: Install a bat box near the building in a location where it can receive seven hours of sunlight. May through August: Allow bats to remain in the building and watch them exit at dusk to identify openings. Sept through April: Seal openings." Ref.: Penn State: A Homeowners Guide to Northeastern Bats and Bat Problems.

As you can see, bats and people can live together quite comfortably, and necessarily. Instead of fearing bats, just enjoy watching them, and hope that they are close by. The benefits far out-weigh the problems.

Information found in Penn State's "A Homeowner's Guide to Northeastern Bats and Bat Problems", Penn State's "Wildlife Damage Control #4".

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