How Bats Work

The gray myotis is a bat species found in the United States. These bats roost in large colonies, mostly in caves. This has made them an easy target for people looking to exterminate bats, since they're easy to find and whole colonies can be wiped out at one time. The gray-myotis population has dropped sharply over the last hundred years, but it is now on the rise again thanks to government conservation efforts.

Photo courtesy Georgia Museum of Natural History

Bat Fact and Fiction

Many people have a negative reaction to bats, and it's easy to see why. Just by virtue of their appearance and behavior, bats play into a number of human fears. First of all, they only come out at night, a time that is full of danger and mystery for humans. Additionally, their leathery wings and odd facial structures coincidentally resemble the grimaces of mythological ghouls and demons.

People are also wary of bats because of the vampire legend. Vampires are a mixture of fact and fiction. There are in fact a few species of vampire bats, and they do feed on blood, but they are not bloodthirsty man-hunters. Vampire bats merely prick an animal or human and lap up the blood that flows out. A powerful anticoagulant in the bat's saliva keeps the blood from clotting, so it will come out in a trickle that the bat can drink from. Vampire bats only need about two tablespoons of blood per day to survive, so they never consume enough to kill their prey, which is generally limited to large animals such as cows and, occasionally, people.

Vampire bats can be dangerous, however, because they sometimes carry rabies and can pass it on to their host. Vampire bats are only found in South America and Central America, and even there the risk to humans is minimal. You are much more likely to die from a bee sting or dog attack than from a vampire-bat bite.

Most bat species are not only harmless to humans, but actually beneficial. Insectivorous bats are far and away the best bug-killers on the planet. The little brown bat, one of the most common North American bat species, can catch and eat as many as 1,200 mosquitoes in one hour. The famous colony of Mexican free-tail bats that lives underneath the Congress Avenue Bridge in Austin, Texas, will eat up to 30,000 pounds of insects in a single night. A Mexican free-tail colony in Bracken Cave, Texas, containing more than 20 million bats, will eat roughly 200 tons of insects in a night. These bats, and many other species, feed on insects that destroy crops, providing an invaluable service to farmers.

How Bats Work

A cloud of bats pours out from under the Congress Avenue Bridge in Austin, Texas. Once considered pests, the bat colony has now become one of Austin's most beloved tourist attractions.

Photo courtesy Big Waste of Space

When there is an outbreak of rabies in an area, people often take extreme and ill-informed measures. In Central America, where vampire bats can be a problem, locals find bat caves and blow them up, killing entire colonies. But the bats that are easiest to find are the beneficial ones -- vampire bats roost in small groups and conceal themselves very well. Considering that just one of these harmless colonies might contain millions of insect-eating bats, this sort of destruction is a devastating loss to the environment.

Bats are also beneficial as plant pollinators. Many species, particularly in the tropical rainforest, feed on plant nectar, gathering pollen on their bodies as they feed. When they fly away, they spread the pollen, helping the plant disperse its seed. Bats are major pollinators of many plants used by humans, including bananas, figs, mangoes, cashews and agave, which is used to make tequila.

How Bats Work

The hoary bat, one of America's largest bats, is also one of its most geographically diverse. Hoary bats migrate as far south as Chile and as far north as Canada's northwest territories.

Photo courtesy Georgia Museum of Natural History

One of the stranger ways in which bats help us out is with their bodily waste. Bat feces, called guano, is rich in nitrogen, making it a powerful plant fertilizer. In the past, people also used this nitrogen to make explosives. More recently, scientists have discovered that a number of enzymes found in bat guano work well as cleaning agents in laundry detergent and other products.

Bats are extremely susceptible to extinction because of their reproductive habits. Most bat species give birth to only one baby per year, so they multiply at a relatively slow pace. Since bats have a fairly long life span (as long as 30 years in some species), the loss of one female bat has a major effect on the rate of reproduction.

Bats are some of the most amazing animals on Earth. They are so well adapted to their environment that they have survived as a group for more than 50 million years, longer than most other modern animals. To learn more about bats, including bat research and bat preservation, check out some of the links on the next page.