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Why/How Do Cats Purr?

The purr is one of the most distinctive features of our feline companions, yet many cat owners and feline enthusiasts do not really know how and why cats do this.  To be quite honest, even us veterinarians do not completely understand the reason behind purring and the physiological mechanism that enables feline purring, but we do have some level of understanding I will be sharing in this article that will shed some light on this feline anomaly.

Kittens begin to purr as early as two days old.  It exists in this early phase of life as a connection to Mom that seems to signal contentment, letting Mom know everything is okay so she can turn her attention to one of several other kittens that may be in greater need of her attention.  It also seems to contribute to the bond between Mom and kitten, as kittens and Mom will often purr simultaneously when in the midst of affectionate interaction.
As the kittens progress into adulthood, we commonly observe that cats will still purr as an expression of contentment, but purring may also occur during times of injury or stress.  In this context, purring seems to be a self-soothing tool that cats may use as a sort of coping mechanism.

As far as how cats purr, that is not quite as clear, but here are a few facts that we do know.  In contrast to the meow which is a vocalization that only occurs on exhalation (expelling air), the purr is a sound which is made on both inhalation (inhaling of air) and exhalation.
Purring emanates through the larynx, a structure that is commonly known as the voice box.  This we know because cats that suffer from laryngeal paralysis lose the ability to purr.  Where it becomes a little bit more mysterious is what differentiates the meow sound that would be more akin to the “voice” of the cat, versus the rhythmic, almost percussion-like sound of the purr.

The answer to that seems to lie in the feline’s internal laryngeal muscles, which control the opening of the glottis (the vocal folds and spaces between them), but exactly how that happens still remains a bit of a mystery.  The trigger is hypothesized to come from a rhythmic/repetitive neurological mechanism of the central nervous system known as neural oscillation.

The cat’s purr is one of the most unique characteristics of feline and to many who love having cats as companions and family members, one of the more enjoyable feline traits.  Like the kitten with its Mom, our cat’s purr to let us know they are enjoying a treat, snuggling, getting pet or brushed, or simply enjoy having us nearby.  Like the kitten with its Mom, cat purring enhances the human feline bond.

Dr. Roger Welton is the President of Maybeck Animal Hospital in West Melbourne, FL and founder/CEO of Web-DVM.net.

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