These bats buzz like hornets to scare off predators

To scare away potential predators, some animals display the traits of more deadly creatures. A Scarlet Kingsnake, for example, bears a red, black, and yellow striped pattern similar to that of a venomous coral snake; harmless butterfly species display the same beautiful splashes of color on their wings as their pest relatives; and nestlings of Amazonian bird species are thought to avoid predation by exhibiting the movement and bright orange hue of a poisonous caterpillar.

These evolutionary adaptations are examples of Batesian mimicry — named after 19th-century British naturalist Henry Walter Bates — when harmless species evade predators by mimicking more dangerous species that their hungry enemies know how to avoid.

Most examples of Batesian mimicry that have been discovered are visual. By comparison, there are few examples of mimicry with sound. “Acoustic mimicry is very rarely documented in nature,” said Leonardo Ancillotto, ecologist at the University of Naples Federico II.

Dr. Ancillotto and his colleagues discovered not only a new case of Batesian acoustic mimicry, but also the first documented case between mammals and insects. In their work, published Monday in the journal Current Biology, they report a species of bat that mimics the buzz of biting insects like hornets to trick owls that might otherwise eat them.

Bats are well known for using echolocation to maneuver through the air and locate their prey, but they also use various social calls to communicate with each other.

“We know that sound is very important to bats,” said Gloriana Chaverri, a behavioral ecologist at the University of Costa Rica and author of the study.

Even knowing this, Dr. Chaverri was fascinated by the discovery of acoustic mimicry. “It’s something really new – they’re using sound to confuse, to fool predators,” she said.

About two decades ago, the idea for this research was born. Danilo Russo, co-author of the study and now an ecologist at the University of Naples Federico II, was a graduate student working to create a database for echolocation calls from all species of Italian bats. While handling one species in the field, the greater mouse-eared bats, he was struck by their intense buzzing. But he had to wait years before he could test the hypothesis that they were doing this to deter predators.

To test whether these buzzing bats actually mimic buzzing insects to evade predators, the researchers focused on hornets, bees and two species of owls common to the bat’s geographic range. Both wild owls likely to have encountered a biting insect and captive-bred owls were included in the study.

The researchers collected data on how the owls behaved when audio of a variety of sounds was played over a loudspeaker. Owls typically moved away from the speaker when they heard a buzzing sound and approached it in response to the social call of a non-buzzing bat. But the response of wild owls was much more pronounced than that of captive-bred owls, supporting the researchers’ hypothesis that the greater mouse-eared bat adapted to escape predators by mimicking sound. biting insects that their predators knew how to avoid.

The researchers also found after analyzing the audio that owls, due to their hearing range, would find bats and hornets particularly similar.

David Pfennig, an evolutionary biologist at the University of North Carolina, Chapel Hill, who was not part of the study, is intrigued by the possibility of adaptation involving species that have diverged from their last common ancestor. hundreds of millions of years ago.

“Mimicry is such a powerful idea in science and in evolutionary biology in particular,” he said. “It shows how you can get remarkable adaptations even among very distant groups.”

Sean Mullen, an evolutionary biologist at Boston University also not involved in the research, noted potential limitations of the work, including the small number of owls used, and said he would be curious to see if – on a larger scale – the data supported the hypothesis.

But he was excited to find out more.

“Anytime we can find examples where evolution may have led to adaptation, that’s further proof of the beauty of life,” he said.

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