Bats jam each other in echolocation battles for food

Blaring a special call at just the right instant ruins another’s sonar-guided swoop

Mexican free-tailed bat

SABOTAGE  Mexican free-tailed bats fight sonar wars, jamming each other’s echolocation signals in competitions to snatch moths out of the night sky.

Nickolay Hristov

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Mexican free-tailed bats make short waaoowaaoo sounds that sabotage each other’s sonar-guided aim in duels over the right to gulp a flying moth out of the night sky.

Tadarida brasiliensis, like other aerial hunting bats, locates its prey by making little calls and listening for any echoes bouncing off a moth. Aaron Corcoran of Wake Forest University in Winston-Salem, N.C., was recording other bat sounds when he picked up the strange wavering sirenlike calls in sequences that suggested that free-taileds might be jamming each other. By standing on a scaffold with a spotlight to watch wild free-tailed bats hunt, and also by playing recorded jamming calls, he found that well-timed calls can foil up to 85.9 percent of attempts to capture a moth. This marks the first example of an echolocating animal routinely jamming its own kind, Corcoran says. He and William Conner, also at Wake Forest, describe the jamming in the Nov. 7 Science.

THWARTED  Three video clips filmed outdoors at night show Mexican free-tailed bats (the larger white shapes) hunting tethered insects (smaller white shapes). The first clip shows a successful midair catch, and the rest show how jamming calls foil the attempts. (Video and audio are slowed to one-twentieth of their natural speed.) Credit: A. Corcoran

Bat jamming signals

A Mexican free-tailed bat’s echolocation calls speed up as it nears its prey (audio slowed to one-twentieth of normal speed).

A bat’s jamming call often keeps a competitor from interpreting its echolocation calls well enough to aim a strike properly at prey (audio slowed to one-twentieth of normal speed).

Credit: A. Corcoran

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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