Flying drunk no problem for bats

Drunk New World bats fly fine under the influence

People can’t do it. When we drink, alcohol impairs all kinds of functions, including our ability to drive or walk a straight line. Bat researchers in work published in the online open-access journal PLoS ONE hypothesized that the same rule would apply to bats: the frugivorous (fruit-eating) types often encounter fermented fruits, meaning that frequently, a meal for a bat comes with the alcohol equivalent of a dry martini.

Sonar unaffected

And the humans–not for the last time–were wrong. Bats flying under the influence of a blood alcohol measuring three times the human legal limit maneuvered just fine in their human-imposed drunk tests. The test consisted of plastic chains suspended from the ceiling, requiring the bats to make their way around and through without a collision. Whether they’d imbibed sugar water or grain alcohol, the world’s only flying mammals performed equally well.

Bats may build up a tolerance

Not all bat species have this capacity. It seems that bats, like people, may vary in their alcohol tolerance. In addition, bat species like the New World bats in this study that encounter fermented fruits all the time may have a better tolerance for alcohol than bats who imbibe only occasionally. Old World bats, it appears, are less able to hold their liquor compared to their New World, daily imbibing cousins.

Alcohol: a previously unidentified force of natural selection?

Humans may have long been aware that alcohol can drive certain choices. And now, the bats may confirm that. According to the study authors, sensitivity to ethanol may have determined which bat species developed where. Just as types of fruit may have influenced the speciation of bats, the bat ability to tolerate–or not–ethanol may also have affected bat adaptive radiation.

Ideas for questions

Bats navigate by sonar, while humans rely primarily on inputs including vision to maintain balance and walk a straight line. Do you think that this difference might help explain why these New World bats don’t show the effects of alcohol in their navigation? Why or why not?

The paper refers to the bat “adaptive radiation.” What is an adaptive radiation, and what are the conditions that are required for one to occur? How did bat speciation exemplify this process?

Other frugivorous or omnivorous species encounter fermented foods, as well. One hypothesis, the Drunken Monkey hypothesis,  is that the smell of fermenting fruit drove primate evolution. Can you find other research describing the influence of ethanol on animals?

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