Just south of New Braunfels is the summer home to the largest colony of bats in the world, where researchers were concerned to discover a deadly bat fungus in Bracken Cave earlier this year.
Home to 10 million pregnant Mexican free-tailed bats, the cave will have an occupation of 20 million bats come June and July, as the maternity colony gives birth to pups.
In February of this year, Bat Conservation International researchers and volunteers discovered the deadly fungus pseudogynoascus destructans in Bracken Cave, said BCI director of Bracken Cave Preserve Fran Hutchins. The fungus, called PD for short, causes white-nose syndrome, which has killed millions of bats in the past decade.
“PD likes to grow in cold places, so it affects bats that are hibernating because if it gets on them, it will grow on their skin and ears and eyes and mouth, and irritate the bat,” Hutchins said. “And it wakes the bat up from hibernation, and the bat uses up too much energy and can end up starving to death.”
Mexican free-tailed bats are a migratory species and will likely not come down with white-nose syndrome. The danger however lies in that they are one of the most travelled bats in North America.
“They become infectors, so they may carry it with them back to caves in Mexico where other species of bats live, species that do hibernate,” Hutchins said. “Mexican free-tails also go all over the southern US, California, Colorado, Florida, all over.”
Even in a single night, Mexican free-tailed bats can travel up to 60 miles to forage for food, Hutchins said.
“They’ll go out all the way as far as Pflugerville in one night and come back, eating agricultural pests along the way,” Hutchins said. “They eat moths, beetles, flies, ants and more.”
BCI researchers do year-round monitoring of the cave and go into the cave four times a year to survey the cave and bats, Hutchins said.
“June, August, December and February, and February was when we found that PD for the first time here,” Hutchins said. “We can’t get rid of it.”
According to the BCI website, www.batcon.org, biologists first saw bats sick with white-nose syndrome in 2007 in three caves near Albany, New York.
“The disease is causing massive population declines for multiple hibernating bat species – resulting in one of the greatest losses to wildlife in the past century,” the website states. “The disease is caused by a fungus from Eurasia, which was accidentally transported here by humans.”
The fungus can spread quickly from bat to bat or from bat to cave to bat, Hutchins said.
“The lifespan of a Mexican free-tail bat is about seven to 12 years, so it’s the same bats migrating, although we can’t say if it’s the same bats returning here every year,” Hutchins said, implying the bats may roost at several different American caves over their lifetime.
The biggest threat to Mexican free-tailed bats isn’t white-nose syndrome, Hutchins said. It’s humans.
“The biggest threat to these bats — and bats in general — is loss of habitat,” he said. “Also thousands of bats and birds are also getting killed each year by wind turbines. We humans build these huge things and stick ‘em right in the wind stream, which is how migrators move, and year it ends up killing a lot of them.”
With how common bats are, it’s important people become educated on them, Hutchins said.
“Humans think all bats drink blood or all bats have rabies — no, only three bats of the 1,300 species eat blood, and very few bats actually test positive for rabies,” Hutchins said with a laugh.
For more information about how to donate to BCI, visit www.batcon.org. BCI members are invited to tours of the Bracken Cave Preserve throughout the summer, Hutchins said. Members are able to watch an “emergence” at sunset or a return at sunrise.
“We call it a ‘batnado’ when they come out of the cave, because they swirl around as they come out and then they scatter out. It takes them about three hours to all emerge.”