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Forget the stereotypes: the mysterious and shy creatures are also some of the most interesting animals from the scientific point of view. We know more closely the secrets of their sonar, the social interactions, the prodigies of flight and the origin of the false myths that surround them.

Bats are the second largest group of mammals. One fifth of all living land mammals are part of the order of Chiroptera (a term of Greek origin meaning "winged hand"). For number, they are inferior only to rodents, and are distributed in all continents, except in Antarctica. Once they were there, too: 42 million years ago bats spread from the Americas to Australia, passing through the frozen continent, which at that time had a temperate climate.

They can handle traffic jams. When they hunt in groups and in crowded contexts, Mexican free-tailed bats (Tadarida brasiliensis) can suppress their own calls to prevent the echo of the sounds emitted from confusing with those of their companions. The social nature pushes them to common sense … almost always: in 2014, a study on the same species published in Science had shown that bats can emit ultrasonic signals that put rival echolocation systems out of action.

Not everyone gets their bearings thanks to ultrasound. Fruit bats do not emit sound waves to identify prey and obstacles. For a long time it was believed that they only sail "on sight", orienting themselves with their eyes, but in 2014 it was discovered that they exploit a different form of echolocation: when they fly in the dark, their wings "creak", and the echo of these clicks helps bats find their way. The sonar of bats may have evolved independently several times over time.

Why crash into the windows? Sometimes, however, this system is "misfiring". For the sonar of bats, smooth vertical surfaces like those of windows are practically invisible. The "blackout" is due to an acoustic property of these surfaces, which reflect the sound waves emitted by the bats far from the animal and are therefore mistaken for free spaces to cross. It could be just the smooth surface (and no other factors) that make the wind turbines insidious for bats. Even the horizontal smooth surfaces send them into confusion: past studies have shown that bats interpret them as "water", which they try to drink.

It has nothing to do with vampires. Only three species of bats on the approximately 1200 notes feed on the blood of other animals. If you find a bat, you will almost certainly prefer a gnat or fruit to your jugular. Bumping into a real Azara vampire (Desmodus rotundus, pictured), a vampire bat common in the American continent, is not sympathetic in any way: the species has developed facial nerves capable of detecting the body heat of prey up to a minimum of 32 degrees, a capacity that was thought exclusive of snakes. Generally these bats attack small vertebrates or cattle, but when humans push too close to their habitats, they can become prey in turn.

# How a hungry bat moves

It is not true that they stick to the hair. The low flight of bats may give the impression that they are headed right for our head, but it is not. In addition, some small bats hanging upside down, before taking flight, drop off for a few moments from where they are perched. Some historians link the birth of the legend to the ancient recommendations made to Christian women to cover their long hair, because they could attract the devil (the bats already had a bad reputation).

# Other historical animal lies

Their immune system remains "on" 24 hours a day. Although provided with a number of interferons (the proteins produced by cells to defend themselves from viruses) much lower than the human one, bats have constantly active immune defenses, even when they do not seem to there are ongoing threats - as opposed to human defenses, which are activated on purpose as soon as they identify an "attack". It is thought that this feature allows bats to control viral infections of which they are vectors (such as coronavirus middle eastern respiratory syndrome, Ebola, SARS) without being infected in turn.

Their wings: an engineering miracle. In addition to a system of over 40 joints that allow the wings to move independently in every direction, and a membrane that multiplies the propulsive force with each beat, bats can count on a very thin network of muscles arranged in the skin of the wings (patagio), which allow you to perform refined and precise movements. The wings have also diversified according to the flight spaces of each species: those that have to avoid obstacles in dark and dark caves have wide and rounded wings that allow rapid changes of direction, but they are not very suitable for long flights in open spaces. The species that make long journeys have more massive bodies and narrower and elongated wings: they take a little time to mesh and curve more with difficulty, but once in flight they bear fatigue better.

We can't do without it. Bats serve a fundamental service for agriculture and global food sustainability. They are responsible for the pollination of about 300 fruit plants and are excellent seed dispersers: greedy of fruits, they then disperse the seeds with guano, even at a great distance from where they ate. Not to mention their undisputed primacy of natural pesticides: it is estimated that each of these animals swallows about 2, 000 insects per night (many of which, fortunately for us, are mosquitoes).

The Bat-cave really exists. On the island of Mindanao, in the Philippines, is the Monfort cave, which houses the largest bat fruit colony in the world: 2 million bats, 640 per square meter.

# 5 more things you may not know about bats

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Bats are the second largest group of mammals. One fifth of all living land mammals are part of the order of Chiroptera (a term of Greek origin meaning "winged hand"). For number, they are inferior only to rodents, and are distributed in all continents, except in Antarctica. Once they were there, too: 42 million years ago bats spread from the Americas to Australia, passing through the frozen continent, which at that time had a temperate climate.