Behind the Recent Spate of Vampire Bat Attacks

A vampire bat hangs out at the Philadelphia Zoo. AP Photo

Bites from rabid vampire bats were blamed for 23 deaths in northern Brazil over the past two months, according to local newspaper reports.

Many scientists fear such encounters will become more common as the bats' forests homes are destroyed and they are lured towards cattle ranches and farms where livestock and humans make easy prey.

But much of what people perceive about vampire bats is myth, and experts say protecting against them is fairly easy.

Food is food

Vampire bats live in subtropical and tropical regions in northern Mexico and throughout parts of South America. There are three species. The one that feeds on farm animals and humans is called the common vampire bat.

Common vampire bats are small. Their bodies are only about as long as a human thumb and they have average wingspans of about 8 inches. Common vampire bats have strong legs and can crawl, hop, jump and even run.

The bats typically feed on domesticated animals such as horses and cattle. In the rare instances when vampire bats attack humans, it's usually because their regular food supply disappears; often the farm animals have been moved or taken to market.

To the bats, a sleeping human is just another large, warm and unconscious animal.

"The people are likely to be bitten by vampire bats are those that sleep outdoors or sleeping in huts that don't have any windows on them," said Barbara French, a bat expert at Bat Conservation International, a Texas based non-profit organization.

Bat myths

Fears about vampire bats are fueled by a lot of misconceptions, French says. A common one is that the bats bite the throats of their human victims. The truth is a little less glamorous.

"They're more likely to go for a person's big toe," French told LiveScience. "There's a good blood supply there and the bite is usually less noticeable."

Also, instead of sucking the blood of their victims as is generally believed, vampire bats make a small tear in their victim's skin and lap at the blood as it oozes out. When the bats have finished their meal, they're often so engorged with blood that they're too heavy to fly. The bats have to crawl off their sleeping victims and go someplace to digest their meal before returning home.

A lot of human deaths could be prevented if people take simple precautions, French said.

"They're not like a rodent, which can dig or chew things apart to get into a building," French said. "If there isn't an opening for it to fly in, the bat just doesn't go in. A simple screen over openings will keep a vampire bat out."

The Dracula effect

Still, fears persist.

"They're nocturnal, people don't tend to know as much about them and what we don't know we tend to fear," French said.

Legends of vampire-like creatures can be found in cultures all around the world. Bram Stroker's fictional character Dracula has served as the template for vampires in modern western culture. It's widely thought that the real life inspiration for Stroker's 1897 character was the Romanian Prince Vlad III Dracula, also known as "Vlad the Impaler," so named because his preferred method of torture and execution was impaling people.

How They Eat

A vampire bat hangs out at the Philadelphia Zoo. AP Photo

The common vampire bat, Desmodus rotundus, hunts at night, when other animals are sleeping. It doesn't suck blood. It uses heat sensors to find a victim's veins. Sharp teeth cut the animal -- about like a shaving nick -- and the bat simply laps up what oozes out.

A chemical in the bat's saliva keep the blood from clotting, so it keeps flowing (a blood-thinning drug developed from vampire bat saliva helps prevent strokes and heart attacks). Another chemical numbs the victim's skin so it won't wake up.

"They sit there licking the wound for up to a half hour," says Daniel Riskin of Cornell University. A bat will drink about a tablespoon of blood in a sitting.

Robert Roy Britt, LiveScience SOURCE: Daniel Riskin, Cornell U.; Wildlife Trust; Woodland Park Zoo in Seattle; Cincinnati Zoo