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