Revamping the Reputation of the Vampire Bat

vampire bat

Scientific studies indicate that the much-maligned vampire bat may hold the key for treating heart disease and strokes. (Photo credit: Kozoriz Yuriy/Shutterstock)

For many centuries, people have associated bats with eerie places. Perhaps its because most bats appear primarily at night and seem to move stealthily in the dark. When most people think of bats, however, they think of vampires. We have Bram Stoker, author of the Gothic horror novel Dracula (1897), to thank for this. After reading a story in a newspaper about the vampire bats of South and Central America that live off the blood of animals, he gave his human vampire the ability to change into bat form. It was a good plot device, as the vampire now easily could attack his victims even if they were in locked rooms on the top floors of large homes all he needed to do was fly through an open window! However imaginative, Stoker didn’t pay close attention to the facts, as he made his vampire bats large, menacing flying animals, whereas real vampire bats bodies are about the size of an adults thumb. And while these bats do feel the need to seek the blood of animals for their daily nourishment, they do not commonly bite humans and are fairly generous in how they interact with others of their species. What is more, study of vampire bats may lead to new medications for treating heart disease and stroke. So, what exactly are these creatures that have so captured our imaginations and how closely do they relate to our visions of the vampire?

The Three Types of Vampire Bat

Vampire bats are native to South and Central America, from Mexico to Brazil, Argentina to Chile. There are three types of vampire bat: the common vampire bat (Desmodus rotundus), which feed of the blood of mammals, the hairy-legged vampire bat (Diphylla ecaudata), which feed on the blood of birds, and the white-winged vampire bat (Diaemus youngi), which feed on the blood of both mammals and birds. Notice that, interestingly, each bat occupies a distinct genus, sharing it with no other species. Unlike fruit-eating bats, vampire bats have short, cone-like muzzles. They have small ears, short tails and front teeth well-suited for cutting. These bats are small, not at all menacing, creatures. With wings fully expanded they are about the size of a candy bar. They also don’t really suck blood from their victims as much as they lap it up with their tongues, which have grooves that carry the blood down their throats via capillary action.

When The Vampire Bats Attack

But, in retrospect, the bats do resemble their supposed human incarnations in the rather peculiar ways in which they stalk and feed on their prey. For one, they are tricky. The white-winged vampire bat, for example, doesn’t brutally attack its victims, most notably chickens, by flinging itself at it. Instead it nuzzles up to the bird, pretending to be one of its newly hatched brood. The bird will treat it as one of its own, even sitting on it to keep it warm. There, the bat has access to the dense network of blood vessels in the chickens underside, a rich source of nourishment. During the feeding process, the bat releases chemicals that numb the bird to the attack. The chicken may never even realize the bat is feeding!

Vampire bats can also be quite agile and speedy. Feeding mostly on cows, common vampire bats have developed the ability to move quite quickly on the ground. They run with a kind of leaping gate and can reach speeds of up to 1.2 meters per second. They prefer to bite the cows in the back part of the leg, just above the hoof, also releasing chemicals that numb the animal to their attacks and can keep them from walking. These bats often will attack sleeping animals, and, again, the animals may never know it.

One myth about bats is that they cant see well, instead relying totally on sonar for navigation. Not true. Bats actually have eyesight comparable to our own and some even see in color. But the one amazing fact about bat senses you might know is that, in addition to a good sense of smell, they actually seem to smell heat. Their noses are loaded with proteins sensitive to infrared radiation. This helps them greatly in stalking prey. There is some evidence to suggest that bats have such finely tuned senses that they may even remember an animal that once provided a particularly good meal and visit that animal again. One negative, however, is that they don’t seem to be too discriminating in choosing what food sources might be bad for them. In other words, they don’t avoid potentially poisonous meals like other animal species do. This could be that they have such limited options for feeding that they’ve never needed to develop this trait. It also could be that, as the diet evolved as a trait in these bats, developing such a discriminating palate would not have been beneficial for survival.

Living on a Blood Diet

The small stature of the vampire bat is a hindrance for the animal not only because they’re not able to defend themselves well, but also because even small of amounts of food, as little as an ounce, render them too heavy to fly. Perhaps this is why these bats have the ability to digest blood very quickly. The linings of their stomachs quickly remove the liquid portion of the blood, leaving only the nutrients that are then digested. Vampire bats digest food so quickly that they often start excreting wastes from their meals even before they’ve completed a single 30-minute feeding period. This could also be the reason why vampire bats have found it quite beneficial to the survival of the species to become generous with their food sources. A vampire bat will often regurgitate food for a fellow bat that might be hungry and unable to find any of its own. While selfishness isn’t something that immediately comes to mind when thinking of human vampires, the free-sharing of food also doesn’t perfectly fit into the image of the heartless bloodsucker.

Vampire Bats are Good for the Heart

Yet, probably the most shocking blow to the vampire’s image comes from research on vampire bats. Scientific studies indicate that the bats may hold the key for treating heart disease and strokes. Along with the numbing chemicals they secrete while feeding, their saliva also contains a strong anticoagulant that helps the blood from their victims flow more freely. A Venezuelan research team has isolated this glycoprotein, and it has been given the name Draculin, in honor of Bram Stokers vampire.

Most anticoagulants employed to treat stroke victims need to be administered within three hours of the stroke, otherwise they can do more harm than good. In one study, however, it was found that Draculin actually might extend that window to up to 9 hours. According to lead researcher Michel Torbey, the researchers hope that the bat saliva, in itself, dissolves the clot with lower risk of bleeding in the brain afterwards.

Although testing is still in its early phases, if effective, Draculin would help prevent ischemic strokes. This type of stroke occurs when blood clots block blood flow to the brain. Ischemic strokes account for 87% of the 795,000 strokes Americans have each year. So, the next time you see a bat disparaged in a movie, now you know the real truth behind these elusive, mysterious, and potentially human-health-benefiting creatures.

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