As I walked up to part of the Africa exhibit at the Oregon Zoo, in Portland, a pair of big brown eyes gazed curiously into mine. They were looking at me upside down; the sleek-furred creature with a foxlike face was hanging by its back feet. It was one of the world's most abundant mammals: bats.
The exhibit contained numerous tree branches, and green mesh spanned its ceiling. Three species of fruit bats hung from the branches and the mesh: a straw-colored bat, an Egyptian bat, and an endangered Rodrigues bat.
"They look just like animals," a woman said as she watched the bats, too. Many of them walked upside down on all fours – on the green mesh. When asked what she thought the bats were, she admitted, "I know they're animals. They just seem so strange."
Bats are the world's only mammals that are capable of true flight. A membrane of skin covers their long front arm and four finger bones, which form the structure of the wing. The membrane is attached to the sides of their bodies and then connects to their back legs. The remaining digit on their front legs is a thumb. Most often when the bats landed after flying, they grabbed a branch or the mesh with their thumbs, and then quickly swung to their back feet.
"There'd better not be vampire bats in here," a girl said as she entered the exhibit with her friends. She didn't need to worry. Only African bats were on display; vampire bats don't live in Africa.
There aren't any vampire bats in North America, either, which is home to more than 40 species of bats.
African bats eat either fruit or insects, but North American bats feed almost exclusively on insects. There are two exceptions: the Jamaican fruit bat, which lives in the Florida Keys, and nectar-feeding bats, which live in the Southwest.
Vampire bats – which make small bites in the feet or ears of animals such as chickens, cows, and pigs, and then lick up the drops of blood – live only in the warm climates of Central and South America.
Many of the straw-colored and Egyptian bats at the zoo hung together in groups. In the wild, many straw-colored bats live in big colonies of up to a million bats.
Some North American bat species also live in extremely large groups, such as Mexican free-tailed bats.
Travelers to Texas can see more than a million Mexican free-tailed bats roosting under the Congress Avenue bridge in Austin. And about 20 million of them live in Bracken Cave, near San Antonio.
It's surprising how noisy bats can be. Some of the bats at the zoo squawked and showed their teeth to push other bats away. Other bats seemed friendly with one another, and groomed other bats or themselves using their red tongues to lick their fur clean. Like cats, bats are clean animals.
To learn more about bats, I talked with Barbara French at Bat Conservation International (BCI), which helps educate people about bats.
Even though there are more than 1,100 species of bats in the world – one out of every four mammal species is a bat – many of them are endangered.
Deforestation (the clearing of trees from forest land) has hurt bat populations.
Bats also have been affected by people who don't realize that they are gentle creatures with a necessary role in our environment.
"Bats help to control insect pests,"Ms. French said. In fact, a little brown bat (Myotis lucifugus) – the most common bat species in North America – can eat as many as 600 mosquitoes in an hour. They use echolocation – high-pitched sounds like sonar – to find the bugs.
Some studies show that the Mexican free-tailed bats that live in Texas's Bracken Cave may eat as much as 200 tons of insects per night. Their bug-eating saves money, according to some environmentalists. It would cost many millions of dollars in pesticides to kill the number of insects that the bats eat. And bats are better for the environment.
"Bats also help to disperse seeds and pollinate plants," Frenchsaid.
In many parts of the world, plants from which we get fibers and food are pollinated by bats.
Bat droppings (called guano) make excellent fertilizer for crops. A sign at the zoo told visitors that bats are so important to the ecosystem that without them, the rain forests of the world might become extinct.
Many people think of bats only at this time of year. It's not certain how they became associated with Halloween, but it may be because they are only active at night. During the day, they go into a "daily torpor" during which their body processes slow down to conserve energy.
Frenchmentioned that bats sometimes roost in crypts in cemeteries, which might be another reason they became linked with the scary holiday.
What can kids do to help save the world's bats? "Educate other kids!" she said. Bats can only keep doing their important work if they are left alone by people who have learned to appreciate these unique creatures.
• Scientists divide bats (order: Chiroptera) into micro-bats (microchiroptera) and megabats (mega- chiroptera). Most microbats have big ears and hunt insects. Most megabats have big eyes and eat fruit.
• Bats are not "flying mice." They are not rodents.
• Some species of bats live up to 30 years.
• The biggest bat is the flying fox, which has a wingspan of up to six feet.
• The smallest bat is the size of a bumblebee and weighs about as much as a penny.
• In Chinese folklore, bats symbolize good fortune.
• Many bats hibernate in fall. Others migrate to warmer climates.
• Bats see and hear quite well; the saying "blind as a bat" isn't true.
• Many species of bats do not live in caves. Instead, they roost in trees, mines, and various types of buildings.
To learn more about bats, visit Bat Conservation International's website, www.batcon.org.