UrbanAnimal

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Dear UrbanAnimal,

Why do cats purr?

Anya

Dear Anya,

It might appear that your question is simple and I can now take a break, put up my feet and provide an answer without much difficulty. As usual, though, it seems to be the "easiest" questions that net the most diverse answers and a whole lot of intriguing theories!

Just about every cat, wild and domestic, uses a vocalization that can be described as a purr. The average domestic house cat begins to purr when he's only 48 hours old. We humans usually think of it as a sign of contentment brought about when our cats are being stroked, petted, fed or happily stimulated through play or socialization.

Mother cats purr, possibly as a means of communication, when feeding or washing their kittens and the kittens purr in response. But cats also purr on occasions when they feel stressed such as visiting the veterinarian, giving birth, physical pain, or feeling uneasy. It's possible that cats defer to the purr during times of stress in the same way humans "go to a happy place" when the dentist's drill approaches an aching tooth. Or it could be a gesture of submission as, "Don't hurt me. I'm not a threat to you."

The mechanics behind the sound are still under debate.

Many believe it's produced through reflex motions of the laryngeal and diaphragm muscles. Others contend it's caused by quick twitching of the larynx muscles, which result in vibration. Or it could be, as suggested by Neil Pederson, doctor of veterinarian medicine and author of Feline Husbandry, initiated within the central nervous system and is purely voluntary in nature.

Zoo employees have noted that cats such as tigers and lions often purr by default. In other words, while resting, regardless of their mood or situation, they purr constantly. If one senses a distraction such as an unidentified sound or the arrival of an interloper, he or she will cease to purr. The other group members notice the sudden absence of one purr and, in turn, stop purring long enough to decide if the distraction requires their attention.

Some cats purr with such enthusiasm that their bodies vibrate while others are so quiet it's almost inaudible, witnessed only by a rapid pulse in their throats. Still others rumble like a truck engine or blast our eardrums with reedy, raspy or shrill tones. Alto, soprano, bass - more than one cat purring in unison can sound like a very unlikely choir!

The sound frequency is between 25 to 150 Hz (cycles per second in a sound vibration), which is an interesting range because some medical studies have shown it can enhance bone density and promote healing.

It's thought to be similar to transcutaneous electrical nerve stimulator or TENS used for pain relief in human beings. Natural healing qualities available only to the feline set? According to some cat experts, the healing power of the purr is the reason cats are able to withstand more physical calamities than other animals or humans. It's the "nine lives" theory.

I have to admit that all the cats I've lived with have astounded me with their ability to survive severe injury, major surgery and a variety of illness.

While researching Anya's question, I found a fascinating account of how music can cause a cat to purr in contentment or howl in horror.

A New York-based cat behaviourist discovered that her cat, Elmo, was able to tolerate car trips if she played classical music while driving.

"Handel is his favourite," she wrote. "He settles down, purrs and rubs his face against the cat carrier. But when I switch to rock, the purring stops and the howling starts."

Perhaps Elmo is simply demonstrating the music/cat connection as suggested by Dr. Albert Schweitzer who wrote, "There are two means of refuge from the miseries of life: music and cats."

As always, the mysterious feline never fails in his mission to confound us humans.

E-mail jacque-newman@rogers.com with a question, comment or suggestion.