Some Bats Buzz Like Hornets to Deter Predators

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Much as some harmless snakes have evolved coloring that mimics that of their poisonous relatives, some bats make buzzing noises that resemble a hornet’s, a new study finds. The authors of the paper, published today (May 9) in Current Biology, suggest that greater mouse-eared bats (Myotis myotis) do this to evade predators. 

The researchers tell The Independent that this is the first instance of Batesian mimicry—where a harmless species imitates another, more dangerous one to protect itself from predation—discovered in mammals. 

After being captured by an owl, the bats’ main predator, the researchers explain that buzzing might distract the predator, giving the bats a chance to escape. Study coauthor Danilo Russo, a biologist at the University of Naples Federico II in Portici, Italy, tells The Independent, “Buzzing might deceive the predator for a fraction of a second—enough to fly away.” 

Barn owl looking at camera

Barn owl (Tyto alba)

Maurizio Fraissinet

The researchers first observed the buzzing almost two decades ago during field experiments in which they caught bats in lightweight nets. “When we handled the bats to take them out of the net or process them, they invariably buzzed like wasps,” says Russo. 

New Scientist reports that it was only recently that Russo was able to find a team of scientists willing to investigate the phenomenon. He and his colleagues began by analyzing the acoustics of the great mouse-eared bat buzzing signal and sounds emitted by a western honey bee (Apis mellifera) and a European hornet (Vespa crabro). The researchers noted that bats emitted a wider range of both lower and higher frequencies, but when the team limited the frequencies to only those that owls could hear, the signals began to appear very similar.

Next, the researchers wanted to test how barn owls (Tyto alba) would react to the bats’ buzzing noises. Through a speaker, the researchers played recordings of the honey bee, hornet, and mouse-eared bat buzzing to both wild and captive owls, finding that in all instances, the owls moved further away from the source. However, when they played other bat vocalizations, the owls approached the speaker. The researchers caution that while bees and hornets likely do sting owls, there’s not enough data yet to make a conclusion about why the owls avoid the buzzing noises. 

Benjamin Sulser, who studies bat evolution at the American Museum of Natural History in New York and was not involved in the study, says he is interested but not surprised by the findings. “If I grabbed a bat and it made a hornet sound, I’d think twice, and I’m not even a bat predator,” he tells New Scientist. 

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