Human Journey

The Hazards of Fly Sex

Photo by Shaul Sitton


Birds do it, bees do it, and flies do it too. However, when flies have sex, they may end up on the menu of a hungry bat. Researchers at the Max Plank Institute for Ornithology observed bats and flies living in a cowshed in Germany. Typically, the flies were nearly invisible to the bats’ sonar at night, but this all changed when flies got busy. During sex, male flies produce noisy broadband buzzing sounds that bats are able to hear and home in on. About five percent of copulating flies were attacked by bats, and most of them were eaten. So now we know why bats swallowed the fly.

This study was published in the July 24th issue of Current Biology.

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Since 2005, Michael has been a librarian at National Geographic.
  • Ima Ryma

    The fly was busy having sex.
    The bat was seeking a night snack,
    And heard broadband buzz sound effects.
    The fly asked for the bat attack.
    And sure enough, when sex was done,
    And the fly flew into the air,
    ‘Twas the last time for sexy fun,
    Now the bat’s internal affair.
    So to avoid a bat’s sonar,
    A fly should try celibacy.
    But that’s just not how most flies are.
    Bats are glad flies are so horny.

    Why did the bat swallow the fly?
    The fly just got that urge – that’s why!

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