Why Do Cats Purr?


A meow may massage the heart, but a purr absolutely soothes the soul. The cat is the only animal that makes a musical humming sound when it is happy. All cat lovers have enjoyed the blissful moment of a purring lap bound feline. The entire animal vibrates with joy. Purring is usually a sign of cat contentment, but you may be surprised to learn that there are other very different occasions when a cat might purr.

Why Do Cats Purr?

An "origin of purr" investigation yields quite a bit of information, some of it inconclusive. Let's begin with a few expert opinions. According to Leslie Lyons, an assistant professor at the University of California-Davis Veterinary School of Medicine, purring is probably the result of an evolutionary advantage for cats. A recent study from the University of Sussex in England theorizes that the cat's purr may have developed as a way for domesticated cats to obtain food from humans. That makes sense, since most rational human beings can't resist a purring cat. All domestic cats purr, particularly when they are nursing their kittens or as a result of social contact (petting, hugging) from their human companions.

It is interesting to note that other species in the cat family also purr, including the Bobcat, Cheetah, Lynx and Puma. There is some dispute over whether the largest cats such as the tiger, lion and leopard also purr. Most agree that big cats can only purr when exhaling and it is not technically related to a domestic cat purr. Some scientists believe that big cats who vocalize through roaring do not have the ability to purr.

Fast Facts About Cat Purring:

  • The purr is distinct from other cat vocalizations because it is produced when the cat is both inhaling and exhaling.
  • The measurable Hertz wave of a cats purr ranges from 25 to 150. At the lower end, a cat's purr has the same vibratory velocity as an idling diesel engine.
  • There have been many studies about the healing power of the purr. It has been proven to lower blood pressure and alleviate depression. As a result, some friendly and placid cats are very effective "therapy animals" in hospitals or retirement homes.
  • The frequency of a cat's purr may also promote the healing of bones. Cats suffer less than other animals from osteoarthritis and other bone diseases.

Although we normally assume a cat purrs because they are joyful, there have been many documented incidents where cats purr after being gravely injured or even when they are close to death. Some speculate that this behavior might be related to the healing power of the purr. The purr may release endorphins, which help soothe or calm the cat during her illness. Mom cats will purr as they are giving birth and continue to purr for their kittens as they nurse. Kittens learn to purr days after they are born and may use the sound to bond with their mother. Purring by sick or near death cats may be a last resort stress reducer. It has been suggested that the purr may be like a "mantra" that helps the cat relax. As much as the purr comforts humans, it also calms the kitty who is nervous or in pain.

How Do Cats Purr?

The physiological origin of the purr is also open to debate. It is not being generated exclusively by the vocal chords like a meow or a howl. It is possible that the sound is generated by the hyoid bone, which is a small flexible bone in the cat's neck. When air is pushed through your cat's voice box, it causes the bone to vibrate, releasing that unmistakable sound. Another theory is that the purr is caused by rapid twitching of the muscles in the larynx. A buzzing hum results from the harmonic air vibrations. The only real fact about how a cat's purr is produced is that there really is no iron clad consensus yet. We can put a man on the moon, but the cat's purr is a perfect mystery to science.

How the cat purrs, or why the cat purrs is a fascinating topic. But for cat owners everywhere, the most important point is THAT the cat purrs. Purring is a wonder and a delight, and has undoubtedly contributed towards making the cat the most popular house pet in the world. As humorist and writer Robert Byrne says, "To err is human, to purr is feline."

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