Bats are dependent upon echolocation to catch their insect prey. But competition for resources is fierce among bats, so they've evolved the capacity to "jam" the signals of other bats to send them off target.

Photo: Nickolay Hristov

As is well known, bats make calls and listen to the echos they return. This allows them to triangulate the location of insect prey, which they then swoop down upon for a tasty meal. Incredibly, some bats can emit signals at frequencies exceeding 212 kHz.

But as a new study in the journal Science shows, echolocation can also make bats vulnerable. Through a series of field and audio playback experiments, researchers discovered that Mexican free-tailed bats emit a specialized sound that jams the echolocation of other bats of the same species. It's just one of 15 known communication, or "social," calls exhibited by the species.

Field experiment set-ups for the field observations (left) and the field playbacks (right).

To make this discovery, a research team led by Aaron Corcoran took video and audio recordings of the bats as they competed for food at two foraging sites in Arizona and New Mexico. Expectedly, they captured the "feeding buzz" — a fast call that gets faster and faster as the bats hone in on their prey in the final moments of an insect pursuit. But they also captured a previously unstudied call that was only made when another bat was nearby and was emitting a feeding buzz.

Spectrograms showing (A) three-syllable jams, (B) one-syllable jams overlapping another bat's feeding buzz, and (C) a close-up of a sinFM syllable from (A).

In a second experimental setting, researchers played back the unknown call in the direction of feeding bats — and it made them 73.5% less successful at capturing their prey, leading the researchers to suspect some kind of inter-species interference is going on.

And indeed, the jamming call disrupts the feeding buzz echolocation, thus interfering with the hunting bat's ability to determine prey position.

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Read the entire study at Science: "Bats jamming bats: Food competition through sonar interference".

Images: Corcoran & Conner/Science

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