Sex Can Be A Very 'Risky Business' For Flies In Bat Territory
July 24, 2012

Sex Can Be A Very ‘Risky Business’ For Flies In Bat Territory

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redOrbit Staff & Wire Reports - Your Universe Online

According to a study in the July 24th issue of Current Biology,  bats eavesdrop on the sounds of fly sex to earn themselves a super-sized dinner deal: two flies for the price of one.  For flies living with bats in a cowshed, sex really could be the death of you.

The study is the first to show that increased conspicuousness to hungry predators is a huge downside 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 totally 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 ended up in bat bellies when they should be invisible to the bats, given the bug hunters' reliance on echolocation.

Researchers began videotaping to determine what was going on with the bats and flies. The location was perfect, a cowshed, where there was an abundance of flies and a colony of bats resided. Those videos show that flies are extremely reluctant to fly at night, and that bats almost never attack flies that are still or walking on the ceiling.

As soon as fly sex started, their risk of being attacked shot 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. The bat attacker successfully gobbled up both flies for a double meal in about 60 percent of those cases.

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."