Mating Flies Face Higher Risk of Death From Predators

Mating has proved fatal, at least for flies that copulate during the night, according to a new study.

Researcher Stefan Greif from the Max Planck Institute for Ornithology and his colleagues have suggested that flies fall prey to Natterer's bats due to a buzzing sound produced by male flies while mating.

Bats have poor eyesight and find their prey only at night-time using sound waves or echolocation. They have very large ears and the sound that gets reflected helps bats identify the object at the correct position.

Flies make lower sounds while they either sit or run on the ceiling during the night. But the echo made by flies is covered by the strong background echo which makes it impossible for the bats to find their prey.

Researchers noted, however, that when flies mate, the male fly made a buzzing sound which captured the attention of the bats. Five percent of the flies were killed because of their sounds and half of them were eaten by the bats.

To find out how the bats capture their prey, researchers analyzed the movements of around 9,000 flies in a cowshed near Marburg, Germany. They found the flies grab the bats' attention through a buzzing sound they produced while mating.

In order to check if the bats were really attacking the flies based on their sounds, researchers placed several dead flies in mating positions. The bats did not attack the flies; but when the researchers played the copulation sound of the flies on loudspeakers, the bats attacked the loudspeakers.

While several theories have suggested that mating creates a higher risk of being killed by predators, very little experimental study has been performed on the context. Earlier studies have shown that some animals have changed their mating behavior to reduce the risk of predators. One such example is that of moths; they change their mating activities in the presence of predators when they hear the echolocation calls of bats.