As promised in Part 7, we will be discussing the most common sound cats make. Besides meowing, chirping, chattering, hissing and growling, that gentle rumble you hear as he breathes in and out is called “The Purr”.
Purring is still somewhat mysterious and frustrating as there is yet to be a definitive statement on what causes the purring noise in cats. Research suggests that a cat’s purr begins in its brain. A repetitive neural oscillator sends messages to the laryngeal muscles, causing them to twitch at a rate of 25 to 150 vibrations per second. Thus, the vocal cords separate when the cat inhales and exhales, producing a purr. To be defined as a purr, the noise must be a continuous sound production alternating between pulmonic egressive and ingressive airstream. In other words, they must make the sound as it exhales and inhales. It has been recorded that cats purr between 20.94 to 27.21 Hz while exhaling and between 23.0 to 26.09 Hz while inhaling.
Interestingly enough not all cats are capable of producing a purr. Big cats such as the lion, tiger, jaguar and leopard are not able to purr due to their having a flexible larynx bone. However, this flexible larynx bone is what allows these large cats to roar. Two big cats that are capable of purring, but not roaring, are the cheetah and the cougar; commonly referred to as a puma, mountain lion or panther. Other wild cats that can purr but not roar are the lynx, cerval and bobcat. The big and wild cats previously mentioned, along with domesticated cats, are able to purr because the hyoid bone (commonly referred to as the ‘tongue bone’) is completely ossified, making it hard and inflexible. This led early researchers to divide cats into “purring cats” and “roaring cats”.
Other animals besides cats are said to purr. These include hyenas, mongooses, guinea pigs, squirrels, rabbits, gorillas and raccoons. Nonetheless, there is some contention amongst researchers as to whether these animals can actually be considered to be purring, given its strict definition
Cats purr for a variety of reasons. A mother and her babies purr to communicate their location since kittens are born blind and deaf. Since kittens cannot hear until they reach 3 weeks old, it is the vibrations caused by the purring that there are sensing. Kittens can purr not long after birth; sometimes as soon as their second day out of the womb. Purring in very young kittens is associated with suckling. The kitten will purr as it feeds from its mother and the mother often purrs back. Older cats purr when they play or approach other cats, signaling they are friendly and want to come closer.
Purring also produces strong harmonics. Most people associate purring to mean happiness or contentment, yet cats are known to purr when they are hurting, sick, stressed, scared or close to dying. It is suggested that cats may purr in order to heal themselves. Frequencies between 20-140 Hz are therapeutic for bone growth/fracture healing, pain relief/swelling reduction, wound healing, muscle growth repair/tendon repair and mobility of joints. The frequency of the purr in sick animals differs from the contented purr of a healthy animal; it may be a way of self -soothing and de-stressing when Kitty feels at her most vulnerable. When they are alone, and there is no one to communicate with, cats might purr the same way a human might sing to themselves when they are alone.
Purring isn’t just good for cats though; it’s also healthy for cat owners! Studies show that cats do a better job of relieving stress and lowering blood pressure and pulse than other pets. In fact, a 10-year study at the university of Minnesota Stroke Center found that cat owners were 40 percent less likely to have heart attacks than non-cat owners—and purring might play a role in that. Purring is an auditory stimulus that people attribute to peacefulness and calmness. This can give us positive reinforcement for what we’re doing and can contribute to the whole relaxation effect when we interact with our cats. Listening to calming, low frequency cat purrs has been found to maintain bone mass and even reverse bone loss in humans.
This is one of the many reasons we at Downtown Tabby Inc are so infatuated with the Magnificent Feline. Stay tuned for Part 9 of our series, where we delve into the interesting facts about your cat’s primordial pouch. No, Kitty doesn’t necessarily need to go on a diet. There is scientific reasoning behind the wobbly bit carried just below the stomach.