Thursday, October 28, 2004

Bat Time of Year

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As Halloween draws near, you’re likely run into more bats than at any other time of year. Not the live ones, of course, but the other kind: bat decals on windows, rubber bats hung on elastic, bat pencil erasers, bat cookies, and more. My six-year-old son got the ball rolling at our house with a black bat he cut from construction paper more than a week ago.

Whether bats are as widely feared and reviled as they once were seems to me an open question. After all, children and the grown-ups who read with them know well the story of Stellaluna, the baby bat who drops into a bird’s nest. Nationwide, people now put up specially designed houses to attract bats to their yards. And the city of Austin, Texas has even embraced bat watching as a tourist attraction. It’s estimated that 100,000 people visit the Congress Avenue Bridge each year to watch the evening departure of the one and a half million Mexican free-tailed bats that roost there.

For the record, though—

Bats are not blind.

Bats do not fly into people’s hair.

Bats do not carry rabies. Like other mammals they can contract and transmit this disease, but cases of humans being infected with rabies as a result of contact with bats are exceedingly rare.

Bats are not flying mice, and this distinction is important for bat conservation. Mouse populations can rebound from catastrophic declines because mice give birth to multiple young and produce multiple generations in a year. Bat populations, on the other hand, do not rebound well. Individual bats may live from twenty to thirty years, but in most bat species pairs typically produce only pup per year.

If you feel an involuntary shiver when you contemplate bats, think about how bats might respond to us.

We’ve got these great big eyes, but in the dark we’re left to feel our way forward with our hands. Bats have echolocation, their own built in sonar, which allows them to detect insects the size of gnats and objects as fine as human hair.

We’ve got these hands with opposable thumbs--to us, the wonder of the world. But can we use them to fly? No way. Bats are the only mammal that can truly fly, thanks to specially adapted arms and four greatly elongated fingers, which are what bats use to spread their wing membranes in flight and fold them at rest.

Come winter we’ve got to work hard to stay warm, but most bats simply hibernate. Say you’re a little brown bat, one of the most common of the twelve bat species found in Illinois. You get to a cave in the southern part of your range that’s cold but not freezing, you let your body temperature drop to about 40 degrees Fahrenheit, decrease your heart rate to five beats per minute, and you hang out from November until March or April.

It should be noted that when bats are not just hanging around they play an important role in the ecosystems they inhabit. All twelve species of bats found in Illinois, for example, feed on insects, including enormous quantities of mosquitoes and agricultural pests.

An adult male little brown bat eats approximately half of his body weight in insects per night. And a lactating female little brown bat eats more than her own weight nightly.

So if the thought of living with bats makes you shiver, think of where we’d be without them.


Articles from Illinois Natural History Survey Reports online:

Indiana Bats in Illinois

Species Spotlight: Little Brown Bat