Mexican free-tailed bats (Tadarida brasiliensis) compete for prey by jamming each other’s sonar, says a new study carried out by Wake Forest University scientists Dr Aaron Corcoran and Dr William Conner.
Mexican free-tailed bats (Tadarida brasiliensis) exiting Bracken Bat Cave in southern Comal County, Texas. Image credit: Ann Froschauer / U.S. Fish and Wildlife Service.
“This is the first study to show that bats actively jam the echolocation of other bats, and it increases the number of known functions of bat sounds to three: echolocation, communication, and acoustic interference,” Dr Corcoran said.
Dr Conner added: “sonar interference has only been observed in Mexican free-tailed bats. It isn’t known if other bat species – or other echolocating animals like dolphins – are employing the same tactic.”
When a Mexican free-tailed bat (also known as Brazilian free-tailed bat or Austonian bridge bat) hears a competitor going in for the kill, it makes a specialized jamming call to prevent its competitor from making the catch. The bats often take turns jamming each other until one of them gives up.
To demonstrate this, Dr Corcoran and Dr Conner had to rule out other possible functions of the call – for example, that the bats were simply communicating with each other.
At the Southwestern Research Station in Arizona and in a high school parking lot in Animas, New Mexico, they recorded foraging Mexican free-tailed bats with cameras and ultrasonic microphones that allowed them to reconstruct the flight paths of the bats from their emitted sounds.
The scientists saw that the bats almost always missed their prey when another bat was jamming them.
They also lured wild bats into trying to capture moths suspended from an ultra-thin fishing line while they played different ultrasonic sounds from a speaker.
The jamming call only caused the bats to miss the prey when it was played at precisely the right time and frequency.
The findings are reported in a paper in the journal Science.
“This research changes our understanding of the possible ways animals compete with each other for food, which is one of the most basic biological needs,” Dr Corcoran said.
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Aaron J. Corcoran & William E. Conner. 2014. Bats jamming bats: Food competition through sonar interference. Science, vol. 346, no. 6210, pp. 745-747; doi: 10.1126/science.1259512
