Flying Under the Influence

Boozing Bats Are Still Expert Fliers

Flying Under the Influence
Fruit-eating bat in Australia. [Credit: Shek Graham, flickr.com]
By | Posted February 15, 2010
Posted in: Life Science Blog
Tags: , , ,

In Central America, where mangoes and palm fruits ferment in the tropical sun, bats are likely boozers. But boozing bats, a new study has found, aren’t stumbling drunks. In fact, a plastered bat is just as skilled at flying as a sober one.

Last April, a team of bat researchers, led by Dara Orbach of the University of Western Ontario in Canada, captured 106 bats representing six different species in northern Belize. At the Lamanai Outpost Lodge, “Belize’s Premier Jungle Logde,” they opened a bat-only wet bar. They served half the bats a cocktail of sugar water and ethanol—the type of alcohol produced when foods ferment—and the other half virgin sugar water.

When they tested the bats’ saliva, they found the ethanol-fed bats had a blood alcohol content (BAC) as high as .3 percent. This is about what your BAC would be if you weighed 150 pounds and drank a 12-pack in an hour. Needless to say, it’s well over the legal driving limit at .08 percent.

But flying bats, unlike human drivers, are superb navigators even when they’re sloshed.

Orbach’s team tested the bats’ flight skills in an obstacle course they built on the forest floor outside the lodge. The course consisted of a large wooden “flight corridor” about the size of a small flatbed trailer. Plastic linked chains hung from the ceiling, spaced little more than one bat wingspan apart.

Remarkably, none of the bats collided with the chains. Nor did they smash into walls or pass out. So the researchers looked for other slip-ups. Did the inebriated bats take longer to complete the course? Did they poop out before making it to the end? Did they fly in circles, dazed and confused?

Sure, a few did. But not any more often than did the sober bats.

The researchers also recorded the bats’ echolocation calls—high-pitched sound waves that bounce off objects—which bats use to locate insect prey and to navigate. They found no measurable difference between the calls of drunk and sober bats. Apparently, a bat can drink a case worth of bat-sized cocktails and not slur its sonar.

Bat experts aren’t certain just how much ethanol a bat consumes in the wild. But their high tolerance for alcoholic snacks means they’ve got more options than other fruit-eating animals. This gives them an evolutionary advantage over lightweights such as the cedar waxwing, a golden-crested North American bird known to die from fermented-berry overdose.

Just when you might be thinking that tanked bats are simply a funny quirk of nature, an icebreaker to save for a cocktail party, consider this: with all the hype around gene doping these days, it may not be long before boozing bats and their high-tolerance genes are back in the news.

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