Some bats buzz like wasps and bees when they are caught, and the sound seems to deter owls.

The results reveal who may be the first known case of a mammal imitating an insectresearchers report on May 9 Current biology.

From 1998 to 2001, animal ecologist Danilo Rousseau conducted field research on larger bat mice (Myotis myotis) in Italy, which included the capture of live animals in fog nets. When he and his colleagues pulled out the bats, they made a buzzing sound in the hands of the scientists, reminiscent of wasps or bees.

“When you hear them, it immediately comes to mind,” said Rousseau of the Federico II University of Naples in Italy.

Years later, Rousseau and his team decided to test the idea that the strange buzzing was not just a coincidence, but instead a type of defense mechanism called Batesian mimicry. Batesian facial expressions are harmless in themselves, but they have a resemblance – visually, acoustically or chemically – to a different kind that is disgusting or dangerous. When cautious predators cannot distinguish harmless imitators from harmful originals that predators usually avoid, imitators are protected.

Researchers caught more of the bats, recording their buzzing cries as they handled them. The team also recorded the buzzing sounds of four species of stinging insects (two wasps and two bees), which are common in European forests.

When Rousseau and his team compared the audio profiles of buzzing insects and bats in the lab, the researchers found that their analysis could distinguish between the two sound sources most of the time.

But the audience matters. brown owls (Strix aluco) and owls (Tyto alba) usually hunt bats, so Rousseau’s team wondered if the birds could be the target of the buzzing performance. When researchers limited their sound analysis to frequencies heard by owls, humming became much more difficult to distinguish – especially for comparisons involving the humming of European hornets (Vespa crabro).

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owls (Tyto alba) have a taste for bats. But the buzzing call some bats make when caught can cause birds to rethink their diet.Maurizio Fraisine

The team then released recordings of the buzzing of bats and insects – and social calls of bats – to eight birds of all owl species in captivity at a wildlife rehabilitation center. The owls reacted to the buzzing of the insect and the bat in the same way, moving away from the speaker. In contrast, they approached the speaker as he reproduced social calls, potentially linking them to loot.

Birds tend to avoid stinging insects, Rousseau said. “When the nests or cavities of trees are colonized by hornets, the birds don’t even try to study them, let alone nest there.” Rousseau and his team believe that this negative association can be evoked in nature if an owl catches a bat and gets an outraged buzz.

This scenario may be the first known example of Batesian mimicry – acoustic or otherwise – when a mammal copies an insect, researchers say.

In general, most examples of Batesian mimicry involve visual cues, so finding potential acoustic mimicry is exciting, says David Pfennig, an evolutionary biologist at the University of North Carolina at Chapel Hill.

Pfennig, who was not involved in the study, cites several examples of acoustic mimicry, such as burrowing owls. imitating the rattle of a rattlesnake or Congolese giant frogs hissing like Gabonese vipers (SN: 25.10.19). But they do not involve the mating of mammals and insects.

The new study makes behavioral ecologist Anastasia Dalziel think of birds other than owls. Songbirds are fairly regular acoustic simulators, said Dalziel of the University of Wollongong in Australia, who was also not involved in the study. “I was waiting for a study like this because bats are very similar in many ways to songbirds,” she says. “They learn their vocalizations like songbirds – at least in some cases – and they can even sing, so it makes sense for me to imitate them too.”

But behavioral ecologist Matthew Bulbert of Oxford Brooks University in England is not convinced that this is a case of mimicry. Owls encounter stinging insects and bats in a completely different context (rest against hunting), which does not make owls likely to be fooled, he said. Instead, buzzing can be generally frightening to an owl, increasing the chance of the bat being released.

“That in itself is still pretty cool,” he says.

These bats buzz like wasps and bees. The sound may deter hungry owls

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