Bats listen for the sounds of flies fucking to catch the prey unawares

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Bats listen for the sounds of flies fucking to catch the prey unawares

If you’re trying to catch flies the easy way, you have to wait until they stop buzzing around in circles like a maniac. The best time to do that is when they’re too busy knocking boots to notice anything around them, which is exactly what bats do. Using their super sensitive hearing, bats wait until they hear the tiny grunts and moans of fly sex and swoop in to get a two for one easy meal.

Based on some old papers, Stefan Greif form the Max Planck Institute for Ornithology knew that Natterer’s bats shelter in cowsheds and sometimes feed on the flies within. What he didn’t know was how the bats catch insects that they shouldn’t be able to find. They hunt with sonar, releasing high-pitched squeaks and visualising the world in the returning echoes. Normally, the echoes rebounding from the flies would be masked by those bouncing off the rough, textured surface of the shed’s ceiling. The flies should be invisible.

And they mostly are. Greif filmed thousands of flies walking on the shed’s ceiling, and not a single one of them was ever targeted by a bat. That changed as soon as they started having sex. Greif found that a quarter of mating flies are attacked by bats. Just over half of the attacks were successful and in almost all of these, the bat swallowed both partners.

It’s not their larger silhouette that gives the mating flies away. When Greif stuck pairs of dead flies onto the shed’s ceiling, in a macabre sexual diorama, the bats never attacked. Instead, the male fly dooms both himself and his partner by being too noisy. As he mates, his wings flutter and release a stream of clicks. Our ears can pick out the low-pitched parts of the buzz, but to Natterer’s bats, the high-pitched portions must sound like klaxons. Greif demonstrated the allure of these sounds by playing recordings of them. When he did, the bats would attack the speakers.

Via