How do cats purr? Scientists have discovered a probable cause
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Scientists have long been unable to understand exactly how cats can make their characteristic purr. One recent study suggests that this may be an automatic process.
Science Alert writes about it.
It is generally accepted that purring is caused by the muscles inside the cat’s larynx. During movement, they expand and contract the glottis – the part of the larynx that surrounds the vocal cords. Therefore, the air vibrates every time the animal inhales and exhales.
Scientists question this explanation. Such low-frequency sounds are usually produced by large animals with longer vocal cords.
A team led by scientist Christian Herbst from the University of Vienna challenged the popular belief that purring causes active muscle contraction.
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Purring may be a passive aerodynamic behavior, the researchers say. It continues after receiving the initial signal from the brain.
“These low-frequency vibrations of the vocal folds include a special voice mode with an extremely long closed ratio, reminiscent of strobes in humans.” scientists say.
Strobe is a type of phonation when the vocal cords vibrate, but are not actually strained. When this happens, we make a low, raspy sound by vibrating the vocal cords at a low frequency.
In animals, everything seems to work in a similar way, allowing small cats to purr even though their vocal cords are much shorter than ours. It uses the same mechanisms that normally produce high-frequency sounds such as meowing.
Collagen and elastin fibers in the connective tissues of the vocal cords are arranged in structures that, like growling cats, dampen the high frequencies of their sounds. These structures, up to 4 mm in diameter, have previously been found in domestic cats, but their role in purring has not been investigated.
To confirm their theory, Herbst and his colleagues removed the larynx, where the vocal cords are located, from 8 dead cats. Then these ligaments were squeezed and warm, humidified air was pushed through them.
During the experiment, all larynxes produced a purring sound due to the independent oscillations of the vocal folds in the range between 25 and 30 Hz. This happened without any muscle contractions or neural information.
At the same time, it is more difficult to investigate the need for muscle contraction in live cats. The team noted that so far the hypothesis of active reduction has not been completely disproved.
Instead, the ultimate cause of purring remains a mystery. Some talk about the pleasure of interacting with people, others – about the healing mechanism.
However, this study, published in full in the journal Current Biology, may lead to new insights into the role of purring in cats.
Earlier we talked about why cats trample you with their paws.
We also wrote about how to understand that your pet is overweight.
Read also: Why cats eat house plants and how to help it
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