Bats mimic buzzing hornets to scare predators away.

Science magazine reveals the first known case of a mammal mimicking insect noises, in a study that found greater mouse-eared bats imitate stinging insect buzzes to keep owls and other potential predators away:

Danilo Russo… [a]n ecologist at the University of Naples Federico II… was conducting fieldwork in southeastern Italy more than 2 decades ago when he snagged some greater mouse-eared bats (Myotis myotis). The species is native to Europe and about the size of a house mouse. Every time Russo went to grab the animals and remove them from his nets, “they buzzed like wasps or hornets,” he says. It seemed like some sort of defense mechanism, he explains.

One of the mouse-eared bats’ biggest predators are owls, which commonly live in the tree nooks or rock crevices that wasps, hornets, and other buzzing, stinging insects hole up in. It occurred to Russo that the bats might be buzzing to mimic bees and send owls scurrying away.

The scientists then set up an experiment in the lab to test predators’ responses to the buzz. They played both the bat and the insect recordings, as well as a control sound from a different nonbuzzing bat species, for eight barn owls (Tyto alba) and eight tawny owls (Strix aluco), which nest in the same crevices as the stinging insects. Half of the owls were raised in captivity, whereas half were wild-caught. The team classified the owls’ reactions to each sound, noting whether they tried to escape, attack, or inspect the speaker emitting the buzz playback.

The birds reacted consistently to both the bat and the bug sounds, darting away from the speaker in response to the buzzing. The wild owls had a stronger response to the sounds, possibly because of their prior exposure to stinging insects, Russo says.

You can read more of Russo’s research here, in Current Biology.