All animals are locked in an evolutionary arms race between prey and predator, with the hunted seeking to evade the hunter.
To avoid being eaten, some creatures become poisonous, some develop camouflage, and others evolve armour. But other animals take a shortcut and, instead of evolving their own defence mechanisms, play copycat and imitate the defences of other animals in order to trick their foes.
Scientists from Italy have found a new example of this tactic in bats, with a European species producing a buzzing sound like a hornet to avoid attack by owls.
Researchers say their discovery is the first case of acoustic Batesian mimicry – when a harmless species imitates a more dangerous one to protect itself – in mammals.
The buzzing may be employed by the greater mouse-eared bat after capture to fool a hungry owl into thinking it is holding a stinging insect, giving the bat time to escape.
Dr Danilo Russo, study author of the University of Naples Federico II in Portici, Italy, said: “In Batesian mimicry, a non-armed species imitates an armed one to deter predators.
“Imagine a bat that has been seized but not killed by the predator. Buzzing might deceive the predator for a fraction of a second – enough to fly away.”
The researchers made the discovery while conducting research in which they caught the bats using mist nets.
Dr Russo said: “When we handled the bats to take them out of the net or process them, they invariably buzzed like wasps.”
Later, the team recorded the sounds and played them back to owls, to see how the birds reacted.
They found that different owls reacted in different ways, probably because of their past experiences with hornets, or hornet-sounding bats.
But the birds consistently reacted to both insect and bat buzzes by moving further away from the speaker, while the sound of potential prey led them to move closer.
According to the researchers, although stinging insects probably do sting owls, there is not enough data to prove this is why the birds avoid the buzzing sounds.
But there is other evidence that birds do avoid noxious insects if they can, so there is precedent for owls to be cautious of animals that buzz.
According to the Bat Conservation Trust, the greater mouse-eared bat was officially declared extinct in the UK in 1990. However, a solitary individual has been hibernating in southern England since 2002, and they are still present in Europe.
The findings are published in the Current Biology journal.
Another example of Batesian mimicry include the poisonous coral snake, which is venomous as its name would suggest, and the king snake which looks very similar but is harmless.
The monarch butterfly is toxic to would-be predators and birds give it a wide berth. As a result of this survival advantage, the viceroy butterfly has adapted over time to look like the monarch, borrowing its toxic reputation.
