BAT’S BEST BET

Biologists check bats for white-nose syndrome. Bats that roost and hibernate in caves are most susceptible to white-nose syndrome.

Native Louisiana Bat Species Provide Valuable Service While Avoiding Disease Plaguing Other Parts Of The Country

story by TREY ILES, LDWF Public Information

Bats, especially those living in Louisiana, get a bum rap. The species that call the Bayou State home are often lumped together with the infamous vampire bat that appears in Louisiana zoos only.

They’re also considered rabies carrying vermin that are to be avoided at all costs. Even when they do get credit for something, eating mass amounts of mosquitoes, it’s a bit misplaced.

But did you know bats are vital to America and Louisiana’s agriculture industry? In fact, bats can be a farmer or gardener’s best friends because of the many insects they devour.

“It’s estimated they save farmers billions annually in crop damage and reduced pesticide usage because of the insects they eat,’’ said Beau Gregory, a Louisiana Department of Wildlife and Fisheries zoologist. “They’re extremely beneficial. We don’t have any fruit bats or nectar feeding bats in Louisiana; all of our bat species consume insects. There is a lot of undue fear out there.”

One thing not to be concerned about is bats looking to dive out of the sky and suck human blood, something vampire movies embellish. True, vampire bats do eat blood. But the species isn’t found in Louisiana and is mostly located in Latin America. The closest they come to Louisiana, which has 12 species of bats, is extreme south Texas.

As for rabies, bats can become infected with the disease and they shouldn’t be handled by humans. But Gregory said the incidence of rabies in bats is very low.

“Bats can contract rabies just like any other mammal,’’ Gregory said. “But since it is fatal, infected bats don’t tend to persist very long in the population.’’

And bats do find mosquitoes quite tasty. But they’ll go after just about any insect.

“There’s a lot of hype about bats and mosquitoes and they do consume mosquitoes,’’ Gregory said. “But the biggest benefit that you rarely ever hear about is their contribution to the agriculture industry nationwide.’’

Agriculture is certainly big business in Louisiana. Gregory said many farmers build bat houses to entice the animal to hang around and take a bite out of the insect population near their crops. He said one citrus farmer near New Orleans has an organic certification, meaning he can’t use pesticides. So he’s constructed several bat houses in his orchard to help with pest control.

With its warm climate and abundance of bugs, Louisiana is a great place for bats.

And it’s a safe place, at least for now, from a disease that has decimated some species of bats in the eastern United States and Canada. White-nose syndrome has killed millions of bats since its discovery in New York state in 2006-07. The fungus that causes the disease, Pseudogymnoascus destructans, has spread rapidly. It has not been found in Louisiana and Florida, the only two states with that distinction in the eastern United States.

“The disease has been detected in Arkansas and Oklahoma,’’ Gregory said. “The fungus that causes the disease has been detected in Mississippi and Texas. So we’re surrounded. Fortunately, Mississippi and Texas haven’t had any mass die offs. So they haven’t had the disease surface even though the fungus that causes it has been found.’’

The disease, named for the fungus which is white and is found on bats’ muzzles, attacks hibernating bats. It has killed more than 5.7 million bats in eastern North America.

A total of nine bat species, including two endangered species and one threatened species, have been confirmed with white-nose syndrome in North America. The fungus has been found on an additional six species, including one endangered species, without confirmation of the disease. Louisiana has five species of bats that have contracted white-nose syndrome in other parts of the country and three that have been found with the fungus but not the disease.

White-nose syndrome appears to be more prevalent in colder climates. The mass die-offs haven’t occurred as frequently in states with warmer weather. And the disease flourishes in caves where bats congregate.

Louisiana seems to have avoided the disease thus far because of its warmer climate and lack of caves. There are only a handful of caves in the state and they are very small. Though bats are found there, it’s a small number, Gregory said. And not all bat species inhabit caves.

“Bats have certain preferences on where they choose to spend the daylight hours and these preferences can vary depending on the species,’’ Gregory said. “Some that would typically roost in caves in other states oftentimes will be in hollow trees in Louisiana. They don’t necessarily have to be huge trees for bats to use them, although very large cypress trees with hollowed out bases can still be found in Louisiana.

“They have also turned to using culverts and certain types of bridges. As we lose more and more habitat - old hollow trees - they’ve even resorted to using attics sometimes.’’

The fungus seems to be easily spread when bats come in close contact with each other in caves. It also seems to only affect hibernating bats. Research has shown that bats have the ability to fight off the disease when awake. The problem is when they hibernate, their immune systems are dormant.

That’s another plus for bat species in Louisiana and a possible reason why the disease hasn’t been found here.

“Because of our warmer climate, bats don’t typically hibernate here,’’ Gregory said. “They do go into periods of torpor, which is similar to hibernation. But it’s not true hibernation and not long term.

“When the nighttime temperatures are in the 50s, which is frequent in Louisiana in the winter, the insects are out flying around. Our bats take advantage of this resource and so they can be found out flying around catching insects as well. When food is available during the winter, bats don’t necessarily need to use hibernation as a strategy for winter survival. That’s one reason that I’m optimistic we won’t have the mass die-offs.’’

LDWF has been conducting white-nose syndrome surveillance for several years. In 2016 LDWF partnered with Texas Tech to survey for the fungus. A graduate student from the university sampled bats and almost 200 culverts across the state.

“That was a pretty extensive survey,’’ Gregory said. “The results showed that the fungus was not detected at any of the locations that were sampled.’’

Gregory said it is certainly conceivable that the fungus will eventually reach Louisiana.

“But I’m hopeful based on the biology of the bats in Louisiana and the biology of the fungus, that we won’t have the big problems that many other states have experienced,’’ he said.

The lack of the fungus has researchers from other parts of the country coming to Louisiana to see if they can find a solution to the problem that can help them alleviate the disease. They are required, however, to make sure all equipment is sterile as the fungus can be picked up and transported fairly easily.

Researchers have cautioned spelunkers to also be aware of the fungus. Though biologists haven’t seen a risk to humans exposed to the disease they say cavers should be careful. A bigger concern is transmitting the fungus from one cave to another.

ADDITIONAL INFORMATION

For more information on
white-nose disease, go to
www.whitenosesyndrome.org

For more information on bats, check out Bat Conservation International’s website at
www.batcon.org

Snout of a healthy bat.

Snout of a bat with white-nose syndrome.

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