To scare away potential predators, some animals exhibit characteristics of more deadly creatures. A scarlet king cobra, for example, wears a red, black, and yellow striped pattern similar to that of a venomous coral snake; harmless butterfly species display the same beautiful patches of color on their wings as their noxious relatives; and hatchlings of Amazonian bird species are thought to avoid predation by exhibiting the movement and bright orange hue of a toxic caterpillar.
These evolutionary adaptations are examples of Batesian mimicry — named after the 19th-century British naturalist Henry Walter Bates — when harmless species avoid 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. In comparison, there are few examples of mimicry with sound. “Acoustic mimicry is very rarely documented in nature,” said Leonardo Ancillotto, an ecologist at the University of Naples Federico II.
Ancillotto and colleagues found not only a new case of Batesian acoustic mimicry, but also the first documented 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 wasps-stinging insects to trick owls into eating 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.
“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, Chaverri was fascinated by the discovery of acoustic mimicry. “This is something really new — they are using sound to confuse, to deceive predators,” she said.
It was about two decades ago that the idea for this research came about. 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 all echolocation calls from all species of Italian bats. When handling a species in the field, mouse-eared bats, he was struck by their intense buzz. But he had to wait years before he could test the hypothesis that they did this to deter predators.
To test whether these buzzing bats indeed mimic buzzing insects to evade predators, the researchers focused on wasps, bees and two species of owls common to the bat’s geographic range. Wild owls that have likely encountered a stinging insect before and captive-bred owls were included in the study.
The researchers collected data on how the owls behaved while the audio of a variety of sounds was played over a loudspeaker. Owls would generally move away from the speaker when they heard some buzzing and would approach in response to the social call of a non-tinnitus bat. But the response of wild owls was much more pronounced than the response of captive-bred owls, supporting the researchers’ hypothesis that the mouse-eared bat adapted to evade predators by mimicking the sound of insects that its predators knew to avoid.
The researchers also found after analyzing the audio that owls, because of their hearing range, would find bats and wasps 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 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. “This 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 learn more.
“Whenever we can find examples where evolution may have led to adaptation, it’s further evidence of how amazing life is,” he said.
