ANN ARBOR—They’ve been accused of sucking blood, eating people and being blind. They range from weighing less than a penny to a two-pounder with a wingspan of six and a half feet, and make up a quarter of all mammal species. Bats, known scientifically by their family name chiroptera, pollinate tropical fruit trees, can each eat 600 mosquitoes an hour, and as a colony can protect a farmer from more than 15 million rootworms in a summer.

Like frogs, bats are a good overall indicator of environmental health; a fact that becomes even more important with the realization that 50 percent of American bats are in severe decline or listed as endangered.

Phil Myers, University of Michigan associate professor of biology, says bats don’t suck blood, but first lick the chosen area with their tongues to desensitize it, then scrape and lap until they’re full. Usually, vampire bats gorge themselves until they can’t fly, Myers says, but have to wait to become airborne until their kidneys filter the material.

Among the variety of bats, eyesight ranges from very good to very poor. Most relay on echolocation rather than sight to find food. This high frequency ultrasound, is higher than the range of human hearing, and generally comes from the bat’s mouth. A few have evolved to emit the sounds from their noses freeing their mouths for eating at the same time. Biologists, using an instrument called a “bat detector” can monitor bat calls which average 30 pulses a second when flying. Once approaching a target, the pulses can increase to 300 a second.

Myers says a bat can tell an object’s size and distance, how long it will take to reach the target and how fast the object is moving. Some bats, he says, even recognize textures, distinguishing stationary moths from tree trunks.

Bats have modified forelimbs that act as “wings” with tiny nails at the end for roosting and feeding. Depending on what and how they eat, bats have long strong teeth to get through rinds and dig deep into fruit or a flap of skin between the hind legs that works like a baseball glove to catch insects. Bats that eat nectar have hardly any teeth, but do have a fluted tongue like a hummingbird’s. Carnivorous bats have thin, sharp incisors to break through skin and tough teeth to tear at the meat.

Because bats generally have only one offspring a year, they are a particularly vulnerable species. When migrating to an area where harmful herbicides and pesticides are still being used, the bat population becomes even more at risk.

In Michigan, bats generally feed at dusk during the summer months. Some of them hibernate during the colder months in protected places like caves and barns. The red bat, able to withstand cold, hibernates in trees. Other Michigan bats migrate a couple hundred miles to southern Indiana while still others head for Mexico.

For more information about bats and other mammals, search U-M’s Museum of Zoology’s Animal Diversity Web at http://www.oit.itd.umich.edu/projects/ADW.

http://www.oit.itd.umich.edu/projects/ADW