Fruit Bats Use Wing Clicks to Find Their Way

Fruit bats, unlike their echolocating brethren, have to use wing clicks to find their way, a new study says.

As nocturnal animals, bats use a form of sonar known as echolocation, combined with a "3D compass" in their brain, to locate and identify objects to avoid crashes. But fruit bats failed to evolve this helpful talent, and so they had to use their own rudimentary form of echolocation instead.

By producing audible clicks with their wings, these "non-echolocating" creatures can use the echoes to guide them through the darkness, albeit with some bumps and bruises along the way.

"When we study extant species of echolocating bats, we see a developed sensory system that has been adapted and improved over millions of years of evolution," Yossi Yovel of Tel Aviv University in Israel, who led the study, said in a press release. "The rudimentary echolocation of the fruit bat is one example of how the first types of echolocation may have evolved."

Though researchers have yet to learn exactly how the bats do it, they aimed to find out if the phenomenon is found among all fruit bats.

During the study, Yovel and his co-author Arjan Boonman selected a total of 19 wild individuals representing three species of fruit bat as well as different parts of the evolutionary family tree. And try as they might to find some other source of their sonar, wing clicks was the only explanation.

"We did all we could to prove it wrong, including sealing the bats' mouths and anesthetizing their tongues, but nothing stopped them from clicking," Yovel said, "except for when we interfered with their wing flaps."

And the darker it is outside, the more feverishly the fruit bats clicked their wings. In a dark tunnel, for example, the mammals increased their clicking rate by a factor of three to five or more.

However, given that this is not a true form of echolocation, it's not surprising that fruit bats frequently bump into things. The fruit bats constantly crashed into thick cables, researchers say, and even with larger objects they failed to come in for a smooth landing.

But though they don't boast true echolocation, their wing clicks still help them frumble through the darkness.

The findings were published in the journal Current Biology.

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