Deception runs rife in the animal kingdom. Defenseless animals will piggyback off the reputation of fearsome fighters in a bid to be left the hell alone – and now, researchers have discovered the first mammal known to mimic the sound of stinging insects to deter predators.
The great impersonator is the greater mouse-eared bat (Myotis myotis) – which at less than 30 grams (1 ounce) doesn’t stand much chance against predatory, 350-gram (12.3-ounce) barn owls (Tyto alba). However, barn owls aren’t great fans of stinging insects and the painful venom their small bodies contain, and here the bats seized an opportunity.
“In Batesian mimicry, a non-armed species imitates an armed one to deter predators,” said co-author on a new paper in Current Biology Danilo Russo of Università degli Studi di Napoli Federico II in Portici, Italy, in a statement.
“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.”
Mimicry is more commonly seen in the visual domain: for example, butterflies that spook small birds by displaying what looks like owls’ eyes on their wings. There are even species still mimicking more dangerous species that are no longer around, such as the scarlet kingsnake (Lampropeltis elapsoides) which mimics the locally-extinct, venomous eastern coral snake (Micrurus fulvius).
Audio Batesian mimicry on the other hand is less common and has never been reported between mammalian and insect species until now. The bats’ vocal deceptions were first observed by Russo who during mist-netting fieldwork noticed that they would “invariably [buzz] like wasps” when being handled.
To test if the “ruse” amounted to Batesian mimicry, Russo and colleagues first compared the distress calls of greater mouse-eared bats to those of four species of insects. They then played recordings of insects and the bats’ impersonation buzzes to barn owls to see how they’d respond.
The owls would consistently back away from the sound of the bats as well as the stinging insects but inspected sounds of potential, non-painful prey. This response was also more pronounced in wild owls who likely had more experience with stinging insects than those participant owls kept in captivity.
The results appear to indicate that the owls’ predatory nature has driven the adaptation of acoustic Batesian mimicry in a mammal copying an insect, and, as Russo says, demonstrates the perplexing and complex nature of evolution.
“It is somewhat surprising that owls represent the evolutionary pressure shaping acoustic behavior in bats in response to unpleasant experiences owls have with stinging insects,” says Russo. “It is just one of the endless examples of the beauty of evolutionary processes!”