Scientists have discovered that a species of bat learned to buzz like a hornet to deter predatory owls from eating them.
This is the first ever case in mammals of what is known as Bates ’mimicry, when a harmless species mimics a more dangerous one to afford protection.
It is also one of the few examples of Bates ’acoustic mimicry, when an animal mimics the sound of another to deter predators.
Morphological mimicry is far more common, such as a fly-like axis with black and yellow stripes and a thin waist.
Scientists accidentally discovered acoustic mimicry when they investigated larger bats with mouse ears, a species native to Europe.
The team caught bats – up to 9 cm long from head to tail, with a wingspan of 40 cm – while conducting field research.
Professor Danilo Russo of the University of Naples said: “In Bates mimicry, an unarmed species mimics an armed one to deter predators. Imagine a bat seized by a predator but not killed. A buzzer could deceive a predator in a split second – enough to fly away.”
The research has been abandoned for years
The professor made the discovery after catching bats in fog nets. He said, “When we caught bats to take them out of the net or process them, they always buzzed like wasps.”
The buzz seemed to be an unusual call for help, and researchers wondered if the buzz was intended as an evolutionary warning to other bats or to deter predators.
However, their initial questions were set aside while they dealt with other research questions for several years until they devised a careful experiment to test their hypotheses about that buzz.
They discovered that the sounds of bat buzzing were acoustically similar to the sounds of insect stings, and then they played the sound of owls in captivity – natural bat predators – to see how they reacted.
“Different owls reacted in different ways, probably depending on their previous experiences. However, they consistently reacted to the buzzing of insects and bats moving away from the speakers. In contrast, the sound of potential prey made them come closer,” the team reported.
The findings provide the first example of mimicry among species between mammals and insects, researchers say.
Most interestingly, when they adjusted their sound analysis to exclude acoustic parameters that owls could not hear, the buzzing of bats was even more similar to hornets.
“Do owls avoid that buzzing sound because they’ve been stung before? Russo says stinging insects probably sting owls, but they don’t have data to prove it,” the researchers said.
“However, there is other evidence that birds avoid such potentially harmful insects. For example, when hornets settle in nests or tree cavities, birds generally will not even explore them and certainly do not nest there,” they added.
The three species included in the study share many of the same spaces, such as buildings, caves, and rock crevices, meaning there are many opportunities for them to interact.
Even so, the researchers said their “intricate relationship” between distant related species was intriguing.
“It’s a bit surprising that owls represent an evolutionary pressure that shapes the acoustic behavior of bats in response to unpleasant owl experiences with stinging insects,” said Professor Russo.
“It’s just one of the endless examples of the beauty of evolutionary processes,” he added, noting that many other vertebrate species also buzz when disturbed – something they plan to explore in future studies.
The research was published in a journal Cell biology.