Mexican free-tailed bats make calls that interfere with fellow bats’ echolocation, causing them to miss their insect targets. Christopher Intagliata reports
Many bats hunt at night—and use echolocation, or sonar, to zero in on their prey. [echolocation clip] That's slowed down 20 times, so you can hear it. But some insects, like the tiger moth, have figured out how to evade that echolocation—by jamming it. "It makes these ultrasonic clicks in the last moment before it would normally be captured by a bat. [clicking sound] And this interferes with the bat’s echolocation, causing that bat to miss.”
Aaron Corcoran, a postdoc at Wake Forest University. Corcoran studied that phenomenon, and says he's now discovered that the jamming strategy isn't limited to prey. Bats do it, too—to foil each others' hunting efforts.
Corcoran and his colleagues recorded Mexican free-tailed bats, Tadarida brasiliensis, echolocating in the wild. And they happened to pick up a sound bats made only when other bats were hunting. [jamming clip] It reminded them of the moth jamming call. So they played back that sound to bats hunting tethered moths, in a field experiment. And sure enough—bats who heard the bat jamming call while echolocating, were 70 percent less successful at capturing the tethered moth, than bats who heard a generic tone, [tone clip] or no sound at all. The study is in the journal Science. [Aaron J. Corcoran and William E. Conner: Bats jamming bats: Food competition through sonar interference]
Of course, if you have a porch light you may be wondering: aren't there more than enough moths to go around? But here's the thing. "The Mexican free-tailed bat has the largest colonies of any mammal on the planet except for humans—with up to a million individuals. So yeah, there's a lot of insects out there but there's a lot of bats to compete with, so they have to find ways to one-up each other basically." Tricky. A real fly-by-night operation.
[The above text is a transcript of this podcast.]