If you are a fly living with bats in a cowshed, sex really could be the death of you. That's according to a study in the July 24th issue of Current Biology, a Cell Press publication, showing that bats eavesdrop on the sounds of fly sex to earn themselves a super-sized dinner deal: two flies for the price of one.
The study is the first to show that increased conspicuousness to hungry predators is a significant cost of sex, the researchers say.
"When mating, the flies utter a burst of broadband, click-like signals, likely from the male's wing-fluttering," said Stefan Greif of the Max Planck Institute for Ornithology. That buzzing sound apparently gives the flies away to bats, which are otherwise completely unable to detect the insects where they sit on cluttered ceilings.
The researchers knew from the start that the Natterer's bats they were studying do eat lots of flies. The question was how those diurnal flies landed in bat bellies when they should be essentially invisible to the bats, given the bug hunters' reliance on echolocation.
As soon as flies start having sex, however, their risk of being attacked shoots up dramatically. On average across four years and 1,100 observed acts of fly sex, about 5 percent of the flies caught in the act by the researchers were also detected and attacked by the bats. In about 60 percent of those cases, the bat attacker successfully gobbled up both flies for a double meal.
Greif says he suspects other predators might use the same strategy to get themselves a two-for-one dinner deal. "Many animals are not only conspicuous in being vocal during sex, but they are also distracted in their attention," he says. Overall, the take-home message is pretty simple: "Sex kills."
Cell Press: http://www.cellpress.com
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