From the Vault June 11, 2002
Even as swarms of monarch butterflies flutter back to the United States from their winter home in Mexico, another less-loved but equally large migration has winged its way north: tens of millions of Mexican bats.
MEXICO CITY (AP) –U.S. schoolchildren fascinated by the orange-and-black butterflies might not go quite so gaga over a wrinkle-nose little flying rodent like the Mexican free-tail bat, now summering in caves and under bridges in a broad stretch of the Southwest from California to Louisiana.
But the bats’ migration is perhaps just as endangered as the monarchs’ — even though bats more directly benefit human beings by eating thousands of tons of agricultural pests and keeping the desert blooming. They even help make tequila.
The bats’ annual October-April migration — the same schedule as the butterflies’ — contains marvels similar to the monarchs, whose successive generations manage to find their way back year after year.
For example, using just chirps and smells to guide her, a mother bat can quickly locate her baby on a cave ceiling crowded with as many as 20 million other bats, while many humans have trouble finding their kids at the shopping mall.
Bats are already becoming a class project at some schools in Mexico, much as monarch breed-and-release programs are in the United States. About 100 million butterflies winter here, and about the same number of bats.
So why the difference in treatment? Both suffer. The monarch is an indirect victim of deforestation. Loggers are cutting down the fir trees it prefers.
But for decades, Mexico’s bat caves — once some of the world’s largest — have intentionally been burned out, bulldozed, poisoned, filled in or covered up. Farmers sometimes set tires alight, and roll them into caves to smoke out bats.
“The problem is truly and simply one of human perceptions,” said Rodrigo Medellin, a biologist and foremost bat researcher at the Autonomous University of Mexico, referring to the bat’s poor reputation.
One reason is the unfortunate overlap of habitat in Mexico between vampire bats — which don’t migrate to the United States — and the insect-eating, people-shy free-tail bat, which gets blamed for the vampires’ attacks.
“A rancher sees vampire bite marks on his cattle, and he goes after the most visible group of bats around, which is almost always a group of non-vampire bats, like the free-tails,” Medellin said.
Vampires are secretive, and roost in small groups of 50 to 100, while other bats nest in groups as large as several million.
It all adds up to a bad rap for the bats.
“When we go into classrooms and ask children what image they have of bats, they almost all say things like, ‘They’re ugly. They suck your blood. They’re the devil’s messengers. They should be killed,”’ said Maria Luisa Franco, an educator who works for the Migratory Mammal Conservation Program.
Using bat games and smiling storybook characters like Marcelo, a nectar-eating bat, and Valentin, a vampire, Franco and her team try to dispel some of the myths and inform children about bats’ useful functions.
Unlike monarch class projects, however, Franco is careful to tell children they shouldn’t enter bat caves or handle bats. And as part of a community outreach program, adults are told how to safely poison vampires.
“It’s a trade off,” said Steve Walker, who, as executive director of Austin, Texas-based Bat Conservation International, helps sponsor the education program and would rather not see any bats killed. “But when you look at the effect (of vampires) on other bat species, it’s worth it.”
Even the tequila industry wants to join the conservation effort, in part to make up for past sins. The link between tequila and bats is found in the endangered long-nosed bat, which is the main pollinator of cactus and agave along its migratory route to the U.S. Southwest.
“Bats are intimately connected to the tequila industry,” said Ramon Gonzalez, director of Mexico’s tequila council. But in the face of the newfound popularity of the drink, farmers of agave are expanding acreage with plants the bats can’t eat.
The long-noses stop at flowering cactuses to eat nectar along their migration, thus spreading pollen from one plant to another, increasing their genetic diversity.
But to catch the distillable sugar that is the heart of tequila, producers have to harvest agaves just before they flower, thus reducing the bats’ food source. Instead of naturally pollinated plants, farmers use farm- or laboratory-produced seedlings, descendants of just a few plants.
Bat advocates are pressing farmers to let just a few agaves flower in each field.
“We want to let the agave flower, but then you lose that plant. It has no commercial value,” Gonzalez said. “We would be quite willing to let some plants flower, but we need to know how many are needed to sustain the bats. We need someone to do a study.”
Consider La Boca Cave, in northeast Mexico, a couple of hundred miles south of the U.S. border. It was once home to what may have been the largest colony of warm-blooded animals in the world, an estimated 25 million free-tail bats in the 1960s. The largest current colony, in Bracken cave near San Antonio, holds about 20 million.
By the early 1990s, the population at La Boca had dwindled to only about 100,000, largely due to vandalism. Teen-agers would enter the cave with flashlights, bonfires, or firecrackers, or pelt the bat-crowded ceiling with rocks.
Such disturbances cause waves of young bats to fall to the floor, where the carnivorous beetles that live in such caves reduced them to skeletons in a matter of minutes.
With the help of bat education programs, the La Boca colony started to revive, reaching about 350,000 in 1996 — when Latin America was hit by a wave of reports of a mythical bloodsucking animal, the Chupacabras, literally “the Goat Sucker.”
Chupacabras was variously described by those who had “seen” it as a kangaroo or turkey with claws, an alien or a panther-like beast. Still, although they didn’t fit the description, bats paid the price.
On one occasion, several adults went to La Boca cave to wipe out the evildoers, the supposed Chupacabras. But they were met at the mouth of the cave by a group of youngsters who had done a classroom project on bats.
It all causes a kind of feeling seldom associated with bats: “It made my heart glow,” Medellin said.
On the Net: