These bats mimic wasps to avoid predators

The tradition is widespread in the animal kingdom.

Some caterpillars can mimic poisonous snakes. The young Amazonian gray sweeper turns into poisonous larvae. Flower flies have evolved to look like dangerous, unpalatable wasps.

All of these examples point to Batesian mimicry, an evolutionary trick that leads a relatively harmless animal to copy more dangerous species to scare off predators.

However, as far as we know, this type of simulation is almost always visual in nature. It is most common in insects, birds, and reptiles.

Now, a kind of vocal imitation was first observed in mammals. A study published on May 9 in the scientific journal current biology He found that a common European species, the great rat bat, appeared to mimic the sizzling of wasps – presumably to avoid being eaten by owls.

“We found that a mammal mimics the sound of an insect to scare off a predator,” says Danilo Russo, lead author of the paper and professor of ecology at the University of Naples Federico II in Italy. “It’s an amazing interaction involving three species that are evolutionarily very distant from each other.”

What is tinnitus?

The largest rat bat, also known as myotis myotis, is a widespread species of European bat that loves to eat insects, especially beetles. These bats live in colonies in woodlands and forest edges, and live in underground caves most of the year, or in buildings during the summer. The large rat bat is often hunted by various birds, including the barn owl (Tito Alba) and owls (strax crazy), especially when they leave or go back to their places.

In 1999, Danilo Russo created a library with echolocation calls of European bats and collected data on how different species communicated with each other. “While I was pulling a tiny little rat bat out of the net, I held it in my hand, but the creature started shivering and making a continuous, intense sizzle,” says Danilo, who is surprised.

“My first thought was… This looks like wasps or bees!”

At first, researchers thought the tinnitus was just a simple cry for help. The sound was so insect-like, says Danilo Russo, that it soon gave rise to a theory. In the end, after several years, researchers decided to test this theory: Do bats imitate wasps or bees?

Danilo Russo himself had already collected regurgitation samples from a barn owl at the entrance to the cave where these bats are located. “Believe it or not, the specimens contained a lot of bat skulls,” Danilo says, when I sensed that it was possible that, from an evolutionary perspective, these bats “made” a very hard attempt to dodge [as corujas] and escape. “

give a peep

In this new study, Danilo Russo and colleagues set out to compare the humming sounds of bats with four different types of hymenoptera insects, including bees (Apis melliferaEuropean hornetswasp crab). The sounds were initially analyzed for wavelength, frequency, call duration, and more, and the researchers found that there was a significant amount of overlap in their structure.

Owls hear a wider range of wavelengths than humans, which prompted the team to adjust sound parameters to suit what the owl was hearing, removing higher tones. The researchers found that the sound emitted by the bats was more like the sound of insects humming to an owl than the sound of humans. “The similarity was especially strong when we removed the variants that owls did not detect,” says Danilo Russo.

Then, through an audio system, the researchers played two insect buzzes for two different types of owls – barn owls and barn owls, including animals bred in captivity and in the wild. One of the sounds was the sound of a bat and the other was what some owls consider to be a social call to the bat.

The reproduction of recorded bat sounds causes owls to approach the source of the sound, but also appears to excite owls. They tried to escape and get away from the columns, but they also tried to check what was happening.

During this experiment, wild owls, who may have had memories of being bitten by a flying insect, were more fearful and were more likely to try to escape than captive-bred owls. Danilo Russo and his team believe this is because captive-bred animals have never been exposed to a stinging insect. However, so far there is little scientific data on how often bees and wasps are infected with owls, or just analysis of whether owls encounter these insects frequently.

“Owls know for sure that this is a dangerous encounter,” says Danilo Russo. Because of this, Danilo argues that this type of batisi simulation could be a technique used when a bat is caught and wants to buy time to try to escape.

future investigations

As is usual with these kinds of new discoveries, there are many open questions.

New studies will have to replicate these findings in the wild, not in the lab, and with larger numbers of owls, to really say we’re dealing with some kind of Batesian mimic, says Bruce Anderson, professor of entomology at Stellenbosch University. in South Africa, which was not involved in the study. Another question is whether owls are not only afraid of the magnitude of the bat’s ringing, as they are with any other unexpected noise. “We might even wonder if this is a case of imitation or just partial sensory exploration,” says Bruce Anderson.

It is also uncertain whether and to what extent the owl fears hummingbirds, although the data indicate that birds generally avoid nesting in the hollows occupied by these types of insects. Researchers also need to understand whether these buzzes are unique to biting insects or if there are other neutral insects that can produce them as well. It would also be positive to test whether owls that have been bitten react with more fear than those that never were, says David Bevenig, a professor of biology at the University of North Carolina at Chapel Hill who was not involved in the study.

While mimicry is common and some cases of Batesian mimicry are well documented, there are many questions about this behavior that are a real mystery, says David Pfennig. That is why such discoveries are important. “Batesy’s simulations reveal some of the best examples of how natural selection can produce remarkable adaptation, even among very distant groups of organisms,” says David Pfennig. There are other examples of vocal mimicry between different species, such as the way owls can produce hissing sounds resembling rattlesnakes, on the other hand, a mammal’s mimicry of an insect would be something unprecedented.

The researchers’ plan is to improve study techniques and expand research.

“Although it is always useful to validate observations made in the field, our results are crystal clear,” says Danilo Russo. “It would be interesting to find similar strategies in other species.” And with more than 1,400 species of bats, plus a handful of vertebrate species other than bats that buzz when alarmed, Danilo Russo thinks other species besides the one studied could also resort to the same trick.

Having animals that live in cavities and mimic frightening sounds as a strategy to avoid predators may already be widespread, says Anastasia Helen Dalziel, an ornithologist at the University of Wollongong in Australia, who was not involved in the study.

Most of what we know about mimicry comes from studies of visual mimicry, however, in principle, mimicry signals can operate anywhere. [tipo] Helen Dalziel says. “It’s really great to have another example of vocal mimicry…to help encourage a broader investigation of mimicry.”

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