Scientists Discover That Bats Use Sound of Copulating House Flies as Cue for Foraging

Posted on July 24, 2012

Scientists have determined that bats listen for the sound of copulating house flies as a cue to foraging. Copulating house flies (Musca domestica) are pictured above.

Stefan Greif from the Max Planck Institute for Ornithology, and colleagues, observed in a long-term study on wild Natterer's bats that the bats like to eat copulating flies in a double-sized meal. The male flies produce a buzzing sound with their wings that can be perceived by bats. Flies that were just sitting or walking on the ceiling did not elicit a predatory response by the bats.

In a community of house flies and Natterer's bats in a cowshed near Marburg, Germany, the researchers analyzed videotapes of the movements of almost 9000 flies. The researchers found that the flies rarely fly at night and mostly sit or run on the ceiling. Finding the flies by echolocation is nearly impossible for the bats as the faint insect echo is completely masked by the strong background echo.

This scenario completely changes when the flies mate. The copulation is a noisy event because males then produce broadband buzzing sounds that can be heard by the bats. Around 5% of the fly pairs that engage in copulation were attacked and mostly eaten by the bats. The researchers say that across four observation years 26% of the observed copulating pairs were attacked.

In order to provide evidence that it is really the sound that makes the flies detectable for the bats, the researchers mounted dead, noiseless fly pairs on the shed ceiling in a position they usually take during copulation. These dead flies were never attacked by the bats.

The research was published here in the journal Current Biology.

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