Hungry bats can tune in to the sound of flies mating to pick out tiny prey that they would otherwise be unable to detect.
Stefan Greif at the Max Planck Institute for Ornithology in Seewiesen, Germany, and his team analysed videos of Natterer's bats (Myotis nattereri; pictured) feeding on Musca domestica flies on a cowshed ceiling. Thousands of lone flies walked across the area without being attacked. However, copulating pairs were attacked 5.3% of the time. Bats also attacked loudspeakers playing the distinctive ultrasound buzzing produced by copulating flies.
This is the first identified mechanism that supports theories that copulation can leave animals more vulnerable to attack.