Bats buzz like bees and hornets to scare off hungry owls

Did you know? Bats mimic the buzzing sound of stinging insects to scare off predatory owls. This type of acoustic trickery, when a harmless animal mimics a dangerous one, has been found previously in some insects but has never before been described in mammals.

Danilo Russo at the University of Naples Federico II in Italy was first struck by the bizarre hum more than two decades ago while working with the bats as a PhD student. “I noticed that when we handled the bats to take them out of the net or process them, they buzzed like wasps or hornets,” says Russo. Only recently was he able to assemble the right group of researchers to investigate the phenomenon.

Russo and his colleagues started by comparing recordings of buzzing greater mouse-eared bats (Myotis myotis) to the hum of insects like bees and hornets. When they limited the frequency of the sounds to reflect how an owl would hear them, the team noticed the buzz of the bats and insects appeared even more alike.

Next, they played a series of sounds to eight barn owls and eight tawny owls, half of which were wild, while the other had been raised in captivity. Each owl heard four noises from a speaker: a buzzing bat, a western honeybee, a European hornet and a non-buzzing bat vocalization.

In all cases, the owls moved away from the speaker when they heard the buzz. The birds moved closer to the speaker for a better look when they heard the non-buzzing bat vocalization!