These bats buzz like hornets to scare off predators

To ward off potential predators, some animals display the traits of deadlier creatures. A scarlet kingsnake, for example, bears a pattern of red, black, and yellow stripes similar to that of a venomous coral snake; harmless species of butterflies exhibit the same beautiful splashes of color on their wings as their noxious relatives; and the chicks of Amazonian bird species are thought to ward off predation by exhibiting the movement and bright orange hue of a toxic caterpillar.

These evolutionary adaptations are examples of Batesian mimicry, named for the 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 cases of Batesian mimicry that have been discovered are visual. There are comparatively few examples of sound mimicry. “Acoustic mimicry is rarely documented in nature,” said Leonardo Ancilotto, an ecologist at the University of Naples Federico II.

Dr. Ancilotto and colleagues have discovered not only a new case of Batesian acoustic mimicry, but also the first documented case between mammals and insects. In their paper, published Monday in the journal Current Biology, they report on a species of bat that mimics the buzz of stinging insects, such as hornets, to fool owls that would otherwise eat them.

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

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

Even knowing this, Dr. Chaverri was fascinated by the discovery of acoustic mimicry. “This is something really new: They’re using sound to confuse, to fool predators,” he said.

About two decades ago the idea for this research arose. Danilo Russo, a 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 the echolocation calls of all Italian bat species. When he was handling one species in the field, the big-eared bats, he was struck by its intense buzzing. But he had to wait years until he was able to test the hypothesis that they did this to deter predators.

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

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

The researchers also discovered after audio analysis that owls, due to their range of hearing, would find bats and hornets to sound particularly similar.

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

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

Sean Mullen, an evolutionary biologist at Boston University who was also not involved in the research, pointed to 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 supports the theory. hypothesis.

But he was excited to learn more.

“Any time we can find examples where evolution may have led to adaptation, it’s more evidence of how amazing life is,” he said.

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