Butt slaps, chin touches… these are all actions that may make your host purr pleasantly, and of course they seem to purr when the cat is satisfied.
However, as humans, we are at a loss as to the true meaning of the “ventrilophony” of meow.
But grunts—one of the most recognizable sounds in the animal kingdom, are also among the most mysterious.
“No one knows exactly how the grunts are made,” said Robert Eklund, a phonetician and linguist at Linköping University in Sweden.
Also, experts have been unable to explain exactly what the grunts mean.
Cats purr when they’re happy, but they also sometimes purr when they’re anxious or scared, during labor, or even when they’re dying.
Cats may be the most mysterious creatures humans welcome into their homes, and purrs may be the most mysterious sounds they make.
At least there’s some consensus on what grunts are.
In the strictest sense, the sound is a rhythmic, rumbling osmosis, consistent with the most typical animal vocalizations, which are made during both exhalation and inhalation, with no gaps in between.
Cats also purr with their mouths completely closed, like a little feline ventriloquist; the sound is emitted from the body at a frequency of about 20 to 150 Hz.
Back in the 1960s, a scientist proposed that grunts are the product of blood permeation through the vena cava, the blood vessel that carries blood back to the heart; this theory was later proven wrong.
Today, it’s widely believed that the source of grunting is the vocal cords: the brain sends electrical signals to the vocal cords, causing them to open and close like little muscle doors.
Many animals can imitate grunting sounds, including bears and guinea pigs.
However, only a few animals are capable of producing a truly gurgle-like, bubbly sound.
In addition to domestic cats, civet cats can purr, as can lynxes, ocelots, and dozens of other smaller members of the feline family.
But lions, tigers and jaguars can’t make the same noise, and scientists haven’t found evidence that any cat can purr and roar at the same time.
Scientists can’t determine what separates grunts from non-grunts.
This may be related to the length, shape or thickness of the vocal cords in some species, or to the tissue structure around them; it may also be due to the stickiness of their hyoid bones.
Perhaps the reason for this has nothing to do with all of the above. Studying purrs isn’t easy: felines generally don’t like to make the sound when they’re in the lab, around researchers.
Whatever the vocal mechanism of purring, it appears to be an innate ability for some felines.
Grunts are a language barrier that we have yet to overcome. In a way, it’s too cat-like.