Cat’s Purr-A Biological Look At A Cat’s Purr
Cat owners are of course familiar with the odd vibrations emanating from their feline friend, though many don’t know how it occurs or even why. To be honest, a lot of the reasons for purring is still speculative. However, evidence seems to point toward the reasons mentioned in this article.
Why Do Cats Purr?
It’s actually not clear why cats purr. Most people think purring occurs only when cats are content, as this is when people are most likely to notice purring. Most of the time, when people see cats it’s when they’re sleeping, being petted, or eating food. However, cats have been found purring even when severely injured and in pain; or while giving birth to kittens. So, there are likely a variety of reasons which a cat might purr. One interesting study that when cats purr when injured, there may be a connection between the vibrations and healing. (Muggenthaler) This sounds like a New Age dream come true, but it’s actually a scientific theory with some evidence to back it.
Perhaps more likely, cats purring while in distress, pain, or giving birth are doing so to trigger the brain into releasing painkilling hormones, which is may be related to the healing; this is a finding from a different study. (Foster)
Another reason for cats to purr is to get something they want, usually food or water. This behavior is found mainly in indoor cats that have a close relationship with their owner, according to one study at the University of Sussex. Purring, coupled with a high-pitched “purr-whine” can get the owner to pour food or water, even at late hours of the night. Many owners, with cats that do this, say it is annoying and they give the cat what it wants, so it will stop it’s whining.
The high-pitched purr is very close to the high-pitched whine of a child, and makes it almost irresistible for owners not to investigate why the cat is making the sound. (Minard)
So, purring might not be linked to being content. It’s possible that purring is associated with something similar to being content around others, and is an attempt by the cat to be friendly to others, or to signal a specific intent. So, when a cat is being petted, asking for food, or even at the veterinarian’s office in a cage and has no way to escape, purring is possibly a way to communicate friendship so that it can get, or continue getting what it wants. For instance, purring encourages its owner to continue petting the cat, to get it food, or in the case of the veterinarian or an injury, to not hurt the cat. In essence, the cat is stating that it is not a threat. (Leyhausen)
The Mechanism Behind the Sound
For the most part, it’s the domestic cat (Genus Felis) which produces the purring sound in its true form. Larger cats (genus Panthera) also purr, but it’s not a “true purr” because the sound is only generated during exhalation, while the true purr of the domestic cat is ongoing with both inhalation and exhalation.
Biologists are fairly sure that the sound of purring comes not from the throat, but from vibrating the folds in the glottis region (see picture). The glottis is the folds associated with the vocal cords, and the space between them. The ability to vibrate these folds are in part directed by muscles in the larynx.
So, the next time a cat owner’s feline friend jumps on his or her lap and begins to make those familiar purring sounds, maybe it’s not because it’s content or satisfied. Maybe the cat just wants something and is trying to manipulate his or her owner.
Holton, Cara and Pires, Jackie. Purring in the Domestic Cat. Fall 2011, academic.reed.edu
Leyhausen, Paul. in Cat Behavior: The Predatory and Social Behavior of Domestic and Wild Cats, translated by Barbara A. Tonkin. New York: Garland STPM Press, c1979.
Minard, Anne. Cats Use “Irresistible” Purr-Whine to Get Their Way. National Geographic News.
Muggenthaler, Elizabeth Von. Felid Purr: A Healing Mechanism. 142nd Annual Acoustical Society of America, American Institute of Physics.