Noisy Fly Sex Leads to Death by Bats
When things get frisky, many animals can get a little noisy at times. For the housefly, loud lovemaking can be a death sentence if they're caught in the act by hunting bats.
The buzzing noise that males make while they mate - made up of fluttering wings and a stream of clicking sounds - can be picked up by bats that are looking for a meal, according to new research detailed this week in the journal Current Biology. The sound dooms both fly partners, male and female, to death by ingestion.
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Stefan Greif from the Max Planck Institute for Ornithology, and colleagues, observed this in a long-term study on wild Natterer's bats that eat copulating flies in a cowshed near Marburg, Germany. The enclosed space offered an ideal experimental setup to determine why the bats attacked flies in the throes of sex.
Over a period of four years, they videotaped and analyzed the movements of almost 9,000 flies, finding that they rarely flew at night - when bats are up and looking for a snack - and when they did move in the dark, they mostly sat or ran on the ceiling of the shed.
For bats, this poses a problem. Finding a sitting fly by echolocation is "nearly impossible for the bats as the faint insect echo is completely masked by the strong background echo which makes them virtually "invisible"," write the researchers.
But when a male fly strikes a fancy for a female fly and sets about mating, he produces broadband buzzing noises that attract the bats. They then follow the sound and get double-sized dinner.
To be sure that it wasn't just the larger silhouette of the coupling flies that helped bats find their prey, the researchers pinned dead, noiseless pairs of flies to the ceiling in the mating position.
The bats ignored the silent pairs. Furthermore, when the researchers played back sounds of flies mating, the bats tried to attack the loudspeakers.
The researchers said this is one of very few studies to show that copulating animals are at a higher risk of being eaten by predators, reports Live Science. About 100 years ago, researchers suggested that mating animals are at higher risk of being eaten by a predator because their attention is diverted and they're more conspicuous. But until now, very little observational evidence have been made to support this idea.
Greif suspects that the flies do the same thing in more natural settings like forests and meadows, according to Discover Magazine. You might expect that evolution would lead the flies towards quieter sex, and that's something Greif wants to analyze next.
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