Bats Use Leaves Like Mirrors to Find Prey in the Dark

Posted on August 18, 2019

Bats have an amazing acoustic hunting ability through echolocation. Scientists have found that leaf-nosed bats can find insects resting silently on leaves in the dark using echolocation alone.

The researchers conducted experiments at the Smithsonian Tropical Research Institute (STRI). The team was led by Inga Geipel, Tupper Postdoctoral Fellow at STRI. The researchers aimed sound waves at a leaf with and without an insect from more than 500 positions. At each position, they calculated the intensity of the echoes for five different frequencies of sound that represent the frequencies of a bat's call.

Leaves both with and without insects strongly reflect back the sound if it comes from straight ahead (i.e., from angles smaller than 30 degrees). When a bat approaches from these angles, it cannot find its prey as strong echoes from the leaves mask the echoes from the little insect. However, Geipel and colleagues found that if the sound originates from oblique angles greater than 30 degrees, the sound is reflected away from the source and the leaves act like a mirror. This approach angle makes an insect resting on a leaf in the dark detectable to the hungry bat.

Geipel says in a statement, "For many years it was thought to be a sensory impossibility for bats to find silent, motionless prey resting on leaves by echolocation alone. This study changes our understanding of the potential uses of echolocation. It has important implications for the study of predator-prey interactions and for the fields of sensory ecology and evolution."

It was previously thought that the leaves and foliage might acts as acoustic camouflage for an insect but by changing the angle of its approach a bat can isolate the weaker echo of a small insect from the echoes of leaves. The insect would need to seek shelter underneath the leaves to avoid detection. A research paper on the study was published in the journal, Current Biology.

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