The "Katzenwäsche" as a phrase belongs to the index. Because how cats treat their fur, has nothing in common with a quick, superficial cleaning. Domestic cats use fur care daily for up to two hours - researchers have now decrypted the smallest details of how they do this and what special role the special tongue tool has.

"Taking care of a cat's coat is a challenge," say Alexis Noel and David Hu of the Atlanta Georgia Institute of Technology, who carried out the study and published it in the Proceedings of the US National Academy of Sciences (PNAS).

This is due to the two layers, "the protective upper coat and the much denser undercoat with shorter hair for warming". To maintain this undercoat, cat tongues on top carry hundreds of barbs of keratin, called papillae, which usually stand back.

With special video technology, the researchers first filmed domestic cats when licking the coat. They identified four phases: the tongue sticking out, the flat unfolding and stiffening of the tongue tissue, the actual licking and the withdrawal, with the tongue curling up slightly U-shaped.

The analysis shows that the papillae set up when the tongue unfolds, thus increasing the contact surface with the coat. When licking the tongue put back on average 6.3 centimeters, at an average speed of 22 centimeters per second - so a single licking process takes significantly less than a second.

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Photo gallery: cleaning miracle cat tongue

Cats compress their fur to reach deep layers

The tongues of the animals carry particularly large papillae in the central front part. This area is crucial: "The larger the papillae, the deeper they can penetrate during the care of the coat," writes the duo. These papillae were on average 2.3 millimeters high for domestic cats. When licking cats then their fur together so that they come to the dense undercoat.

Inside, the papillae have a cavity through which cats bring saliva into their fur. At each licking, the animals distribute the liquid in the coat, after which the cavities fill up again. The saliva contains enzymes that could dissolve blood and other contaminants. "In addition, the saliva cools the skin during evaporation," the researchers write.

During the day, a domestic cat with its 290 papillae can distribute 48 grams of saliva, they calculate. Overall, the coat care contributed to about a quarter of the thermoregulation of the animals. A real miracle tool, the cat's tongue.