Vampires Prey on Panama
Cattleman Francisco Oliva was on a roundup -- of vampire bats. After a swarm of the blood-slurping creatures divebombed his herd and drank their fill one recent night, he corralled several dozen of them in special contraptions that look like giant badminton nets.
He put each bat in a cage and then brushed a poison called vampirin on their backs before releasing them. Back in the bat roost, the animals would be groomed by as many as 20 other bats, causing their deaths. Or so Oliva hoped.
“We have to look for answers, because this little animal is very stubborn,” Oliva said days after the capture as he surveyed his 300-head herd, most of it bearing fang marks and red stains from the nightly bloodletting. Oliva said he would exterminate every single bat if he could.
“You keep the good and get rid of the bad,” the rancher said, philosophic but wearied by the attacks, “and these little devils are terrible.”
More than 100 miles away, on an island research station in the middle of the Panama Canal, Stefan Klose begged to differ. He not only stuck up for Desmodus rotundus, the scientific name for the most common vampire bat, but described the animals as boons to humanity. Research involving bats led to the development of sonar and anticoagulant drugs that prevent heart attacks, he pointed out, and scientists are just beginning to understand the creatures.
“I certainly defend vampire bats’ right to a place in the ecosystem,” said Klose, a young German zoologist who does fieldwork at the Barro Colorado tropical scientific center run by the Smithsonian Institution. Man’s irrational reaction to vampires, he said, reflects “our primal fear of being someone else’s food object.”
Few animals inspire the repugnance and fascination of vampire bats, and perhaps nowhere are opinions more divided than in Panama, which has 120 bat species. Bats are found everywhere in the world except Antarctica, but they thrive in the tropical rain forests that cover much of Panama because of a plenitude of animal and plant foods, abundant shelter and a lack of seasons to inhibit regeneration. In a tropical environment’s biodiversity, bats “have more niches to exploit,” Klose said.
On one side of the debate over the creatures are farmers such as Oliva faced with an escalating plague, and on the other are scientists who use bats and the scientific breakthroughs they have inspired to promote biodiversity.
“Bats have developed a radar system that can distinguish the tiniest insect in the middle of dense bush in the dead of night,” said Todd Capson, a Smithsonian staff scientist who tracks the development of technology derived from tropical flora and fauna. “It’s inconceivable there isn’t something more to learn from that.”
But the benefits of bats are a tough sell here. Sabine Spehn, another German researcher who recently did fieldwork in Panama, said by telephone from the German city of Ulm that her efforts to explain “the nice things about bats” to Panamanians, such as insect control and seed and pollen dispersion, came to naught.
“The response I got was always, ‘The only good bat is a dead bat,’ ” Spehn said.
The antagonism of rancher Oliva is understandable. Here in the remote and hilly southwestern corner of Panama, he and other cattlemen wage a constant battle against a variety of livestock nemeses such as coyotes, crocodiles, ticks, worms and tropical diseases. He has been driven to the edge of desperation by the increasing bat attacks.
Vampire bats have always been present in Panama and their attacks have ebbed and flowed. “But now the bad cycles have become more frequent,” said Argis Barrios, president of Panama’s National Cattlemen’s Assn.
Scientists theorize that the increased attacks on livestock are the result of logging that has flushed the bats out of food-rich forests, and to the growth here in Tonosi of cattle herds, a ready-made and usually stationary food supply for the bats. “The problem is a man-made one,” Spehn said.
During April alone, Oliva said, he lost 10 calves to anemia caused by successive bat attacks. He and other cattlemen bemoan the scarcity of the bat-catching nets, which are strictly controlled by the federal government to prevent their being used to capture endangered birds.
Catching vampire bats with the nets and poisoning them is legal. But Japan, which donated the net Oliva used, has stipulated that a veterinarian always be present to save “good,” or non-vampire, bats caught in the webbing, and there are just three vets in the entire Tonosi Valley region, which is about a quarter the size of Yosemite National Park.
Non-vampire bats make up the overwhelming majority of the 1,100 known bat species. Even the scariest of bats, the giant flying fox of New Guinea, which has a Dracula-like wingspan of more than 5 feet, feeds only on fruit and insects. There are only three blood-sucking, or vampire, bats.
“The problem is there are many bats, many cattlemen and very few nets,” Oliva said as he examined his pockmarked cattle. Several of his surviving calves were anemic -- they had a skin-and-bones look and were weak and unsteady on their feet.
Even on nights when none of the herd dies, Oliva estimates, bats consume or cause the loss of 300 pounds of blood from the cattle, or one-fourth the body weight of a mature steer. The attacks also cause the cattle to weaken and become more susceptible to diseases, he said.
Adult vampire bats, which have a wingspan of 8 inches, swoop down by the hundreds over his herd, the rancher said, landing on the ground and then jumping on the animals’ legs, bellies or faces to bite them. The bat’s saliva contains an anticoagulant that makes blood flow freely.
After an attack on Oliva’s herd last month, the bats were so stuffed they could fly only a couple of feet off the ground, he said, enabling him to catch 87 of them in the special nets that encircled his herd.
Farmers like Oliva may curse the vampires’ very existence, but researcher Rachel Page, a scientist from the University of Texas at Austin who is conducting acoustic research on bats at the Smithsonian’s Panamanian island facility, talks of them with admiration.
Vampire bats, she said, are one of the few animal species that demonstrate “altruistic” behavior. Bats that have been successful in foraging for blood regurgitate it and give it to roost-mates who were unsuccessful in the search for the nightly meal, she said, explaining that the bats must have blood every night or they can die.
Bats’ grooming habits -- licking one another’s backs to remove mites -- is another example of their “highly social” behavior, Page said.
It is also a trait that makes them susceptible to poisoning. “Poisoning them this way is effective but not very nice, because it takes a long time for the bats to die,” said Spehn, the German researcher.
Klose also confessed to a fondness for the creatures. The scientist said feeding time, when the bats accept bits of banana from his hand, is a “really sweet and peaceful sight. It always reminds me of how close these animals are to us and how incredibly intelligent they are -- certainly more exotic and wilder than my neighbor’s dog, but no less smart or cuddly. A flying dog with radar would be impressive, but unfortunately the bats got those traits first.”
Although only a few bats are vampires, the public generally fears all of the tiny mammals, and for no good reason, Klose said. “The reaction is rooted so deeply in human nature it’s hard to get rid of,” he said. “The message is, get over it.”
Easier said than done, say the cattlemen, who point out that bats can spread rabies. Although areas such as Tonosi have been hit harder than others, the cattlemen’s association says 5% of the nation’s 1.5 million cattle were attacked last month, the most in memory.
Although attacks on humans are rare, two Tonosi residents, Felipe Sanmaniego and Juvenal Diaz, reported being bitten by bats as they slept this month. Their blood losses weren’t serious.
“When they can’t find cows, vampires go after horses, pigs, chickens and humans -- anything with blood,” said David Torralba, a technician with the Tonosi office of the Agriculture Ministry.
Though he sympathizes with the cattlemen, Klose says further study of bats might yield more technological breakthroughs.
“Who would have thought reef sponges could lead to anti-cancer drugs, that the scales of butterfly wings could help bring about better kinds of paint? But they are being studied for it,” Klose said. “In fact, very little of what we have invented has been made from scratch. Nature usually provides the template.
“Vampires could hold the key to a problem we want to solve, like AIDS or cancer. But if you destroy them, they are lost for eternity.”
Eternity is beyond Oliva’s range of vision just now. He has an emaciated-looking herd of cows to deal with.
“We’ll take revenge ... if we get more nets,” he said. “But I have to stick it out. There is nothing else I can do.”
Kraul was recently on assignment in Panama.
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Creatures of the night
Vampire bats live in the tropical and subtropical areas of North, Central and South America. Colonies range from about 100 to as many as 2,000.
- Live about nine years in the wild, up to 20 in captivity
- Mate year-round and generally have just one offspring per year
- Seek prey in the early evening; generally travel no farther than three to five miles
- Fly about three feet off the ground; approach prey on foot
- Bats can see, but they locate prey with a combination of smell, sound, echolocation and heat sensing
- May consume up to 60% of their body weight
- Require two tablespoons of blood per day
- Don’t actually suck blood, but make a small incision and lap the bleeding wound
- Thin stomach walls expand to accommodate a large stock of blood
- Saliva ingredients prevent prey’s blood from coagulating and inhibit vein constriction under the wound
- Social grooming usually occurs between females and their offspring and adult females
- Females that have successfully fed will share blood by regurgitating it to hungry bats
Sources: San Francisco State University; www.enchantedlearning.com; National Geographic Society; www.batconservation.org, www.scz.org, ESRI.
Graphics reporting by Tom Reinken