Bats are masters of echolocation, a skill that allows them to identify objects around them using sound.
But not every bat species tunes into this superpower the same way.
Scientists are just starting to understand the anatomical hallmarks of two major bat lineages — a factor that could teach us how echolocation evolved.
Sherri and Brock Fenton
As described in the journal Nature, researchers analyzed the inner ear canals of 39 species of bats.
Bruce Patterson/Field Museum
ilbusca/DigitalVision Vectors/Getty Images
They found distinct differences between the ear structure of bats in two main branches of the family tree: Yinpterochiroptera (“Yin”) and Yangochiroptera (“Yang”) bats.
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In Yin bats, a thick-walled canal encases the spiral ganglion, which is a cluster of nerve cells.
This is a similar structure to human ears, as well as other mammal species.
But for Yang bats, that canal has no wall at all.
The spiral ganglion doesn’t have to pack into an enclosed space, allowing nerve cells to organize and connect to the brain in distinct ways.
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Here’s what ear canal walls look like in different bat species.
April I. Neander
And this is how nerve cells are distributed, depending on the presence or absence of a canal wall.
April I. Neander
Yin bats tend to rely more on a specific set of frequencies for echolocation, while Yang bats listen to ones that vary.
Bruce Patterson/Field Museum
Bruce Patterson/Field Museum
Most echolocating bat species — 82 percent — come under the Yang branch.
This suggests that their ear anatomy may have helped diversify bat species.
Bruce Patterson/Field Museum
The existence of such drastically different anatomy could also shed light on bat evolution.
One big question researchers want to answer: Did both bat lineages develop echolocation on their own, but in different ways?
Bruce Patterson/Field Museum
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“These are different ways of achieving the same goal. It’s like these two types of bats are speaking different dialects of a language.”