Science / Medicine : Vampire Bats : Creature That Inspired Dracula Tales Found Not to Deserve Vile Image; Bat Studies May Aid Man
It’s probably the most loathed mammal on the planet.
Although only a few inches long, with the fewest teeth of any bat species, the common vampire--the Latin American blood-eater that inspired the 1899 tale of Dracula--arouses more horror and hatred than any other creature in the animal kingdom except, perhaps, snakes.
But the vampire’s true life story, new research shows, is far more intriguing than the myths it inspires. As it turns out, the vampire is really--well, a very nice animal.
A recent field study reveals that the vampire does something that Dracula’s author never suspected of such an “ignoble” animal: It shares blood meals with roost mates in need, a very rare and sophisticated form of altruism.
Even vampires’ gruesome feeding preferences may well have a silver lining. Medical researchers now believe that an anti-clotting substance in the bat’s saliva might lead to a new heart drug that could be used to save human lives.
“There are a lot of ironies about vampire bats,” said Paul Robertson, Bat Conservation International’s director of special projects. “The reality of the animal is completely different from almost everything people believe.”
Even though the common vampire does live exclusively on blood, the little bat is no monster. Rather, the vampire is the Gandhi of carnivores: The bat doesn’t kill its prey, and most of the time doesn’t even hurt it. The vampire mostly obtains blood meals from cattle and horses--animals 10,000 times its size that don’t miss the stolen blood. A sleeping cow won’t even wake at the bat’s quick, shallow bite.
The vampire is also generous: “Vampire bats have evolved a system of food exchange” in which they share blood meals with hungry roost mates, Gerald Wilkinson, a University of Maryland biologist, reports. “Only a few species--wild dogs, hyenas, chimpanzees and humans--are known to display such behavior,” says Wilkinson.
For five years, Wilkinson spent two to six hours a day lying on his back, with his head thrust inside the opening at the base of a hollow tree, peering upward at roosting vampire bats in Costa Rica. From this uncomfortable position, he observed hungry bats begging food from vampires that had returned the night before as blood-bloated as carnivorous tennis balls.
The beggar would approach, lick under the round bat’s wings, then the lips. If the request was honored, the donor would cloak the recipient with its wing, and then regurgitate blood directly into its mouth--all this accomplished as both bats were hanging upside down.
From hundreds of hours of watching more than 600 individually banded vampires, Wilkinson saw a pattern. Females fed blood to their own young, which was no surprise. But adult females also fed other “favorite” adult females, who would often return the favor. These individuals were not always genetically related. Instead, they were, as Wilkinson puts it, “friends” who tended to share roosts. Their friendships may last throughout the vampire’s lifetime of about 18 years.
“Vampire bats are extremely intelligent, and really social animals,” the researcher said. “Marvelous little animals.”
If you still aren’t impressed, consider this: One day a vampire might save lives.
Far from the hollow-tree bat roosts of Costa Rica, scientists at Merck, Sharp & Dohme Research Laboratories in West Point, Pa., are investigating how vampires’ feeding methods could protect human hearts.
A vampire’s saliva is more than ordinary bat drool. It’s a virtual medicine chest: A natural anesthetic keeps the prey from even noticing the bite, and an anti-coagulant keeps blood flowing from the prey for up to six hours--enabling several vampires, one at a time, to lap leisurely at the wound for up to 30 minutes each over the course of the night. (One study, conducted in Costa Rica in the 1970s, found that because several bats can feed sequentially from a single wound, a colony of 100 bats may need bite only 3 cows in one night.)
Blood clots don’t just threaten to spoil vampires’ dinners; they also cause heart attacks in humans, when the clot blocks flow to the heart. This is what led Merck to search for anti- clotting agents--and to look at bat saliva. And it turns out, according to Merck scientist Stephen Gardell, bat saliva is 20 times more powerful than any anti-clotting substance manufactured to date. Bat saliva could, he said, could “prove more effective than anything now available” for breaking up clots that cause heart attacks.
Anti-clotting agents now available (including aspirin and Genentech Inc.’s Activase) have another drawback: They may cause unwanted bleeding. Scientists think this may not be a problem with vampire saliva because one of the proteins isolated from the secretion becomes active only when it encounters a clot.
Gardell says more testing is needed before any component of bat saliva can be used to treat heart attacks in humans. But even if it doesn’t pan out, he said, information about the structure of the active protein could help researchers reformulate current drugs to make them safer and more effective.
Ironically, the protein under investigation may also account for why vampires inspire such loathing. Because blood flows for so long from a vampire wound, the blood-stained coats of bitten horses and cows make it look as if the animals have suffered a vicious, gruesome attack. The little bat is considered Latin America’s most destructive predator, inspiring decades-long, multimillion-dollar eradication campaigns.
In fact, says Robertson, who has served as a consultant to vampire-ridden countries, the common vampire hardly ever causes economic damage to the livestock industry. Past rabies epidemics among cattle, once blamed on vampires, are now thought to be the fault of rabid dogs. The worst problem the vampire causes is only indirectly the bat’s fault: Its bites attract flies and the wounds can become infested with screw worm--which, if untreated, can kill a cow.
A further, and sadder, irony is that while the vampire seldom suffers from human eradication measures, millions of other bats do. Although a poison specific to vampires is available, Latin Americans most commonly dynamite caves instead, and end up killing helpful insect- and fruit-eating bats instead of vampires. At least 6,000 caves in Brazil alone were dynamited into rubble in one recent vampire raid, Robertson said, and “almost everything in there was a non-vampire.”
But old myths die hard. Robertson recently saw a Latin American billy goat wearing a woman’s bra around its testicles. Its owner explained the undergarment was to protect the goat’s organs from vampire bites. And the bra had an added anti-vampire feature, the farmer explained: It had been amply smeared with garlic.
BAT FACTS
Bats are the only mammals that truly fly. Here is a look at the common vampire bat: SIZE:
* About as big as a sparrow.
* About three inches long with a wingspan of seven inches.
* Adults weigh half an ounce to 2 ounces.
APPEARANCE:
* Grayish-brown fur
* Short, pig-like snout, pointed ears, no tail.
WHERE FOUND:
* From northern Mexico south to central Argentina, in both arid and forested areas.
* No vampire bats in Europe, despite the legends.
COLONIES:
* Usually contain about 100, but may range from as few as six bats to more than 2,000.
HABITAT:
* Mostly caves, but may be other retreats of near-darkness, including old wells, mine shafts and hollow trees.
MOVEMENT:
* Leaves roosts after dark, usually most active before midnight.
* Navigate by echolocation, emitting a series of supersonic sounds that bounce back from other objects,
* Also capable of walking, running and hopping.
FEEDING HABITS:
* Feeds on fresh blood of sleeping mammals, especially horses, cattle, pigs, and, occasionally, humans.
* After making a tiny bite, a bat laps up about a tablespoon of blood in 30 minutes.
* Bat saliva contains natural anesthetic.
* Can pass on rabies if infected.
OTHER BATS:
* Most bats feed on insects or plants; only vampire bats feed on blood.
* At least 800 different species of bats exists worldwide.
Myths and legends:
Superstition about bloodsucking creatures has haunted humankind for ages, long before the discovery of the vampire bat.
European versions were based on tales of ruthless people who hideously mutilated and drank the blood of their human victims. The word vampire, of Slavic origin, was first applied in Eastern Europe to supernatural beings who allegedly rose from the dead to suck the blood of sleeping people.
When European explorers returned from Latin America to Europe in the 1500s with tales of flying bats that lived on blood, such reports became enmeshed with ancient vampire lore. Stories emerged about bloodsucking European bats--though the vampire species never lived there.
SOURCE: Walker’s Mammals of the World; Macmillan Illustrated Animal Encyclopedia ; Natural History of Vampire Bats ; Man, Myth & Magic--The Illustrated Encyclopedia of Mythology, Religion and the Unknown. Compiled by Times researcher Tracy Thomas
