Why Cats Purr and What They’re Trying to Tell Us

Is there anything more blissful and soothing than the sight and sound of a purring cat? Common knowledge says that a purring cat is a happy cat.

But hold on. Research shows that isn't always the case.

Your kitty's purrs can be a sign of something wrong. To help you better understand your cat's purring pattern, we try to solve the millennia-old riddle around why cats purr.

An Old Question

Cats have lived alongside people for 12,000 years. Worshiped as gods, employed as pest controllers, and invited into homes for companionship, we have built strong ties with these remarkable creatures.

In ancient Egypt, they didn't wonder why cats purr; they accepted this feat that no other animal could perform as part of the deity of cats. But in the thousands of years since, the search for an answer has been on. Recent scientific discoveries have finally given us a clue.

Can All Cats Purr?

Domestic cats purr. So do lynxes, cougars, bobcats, cheetahs, and pumas. What they can't do is roar.

And guess what? The cats that roar (lions, jaguars, leopards, and tigers) can't purr. The difference between these two groups of cats lies in the voice box.

The Mechanics of Cat Purring

The best place to start understanding why cats purr is to understand how cats purr.

The larynx (vocal box) in cats that can purr has a unique feature: air can pass through the laryngeal muscle and cause them to vibrate. Big deal, you might say, that's how cats, humans, and other mammals make vocal sounds or "speak."

Here's where cat physiology differs. First, cats can control the laryngeal muscles so that air around them vibrates at low and constant frequencies. Second, they make the air vibrate duration inhalation and exhalation.

That's unique. We humans and most other mammals can only make noise during exhalation unless you train yourself otherwise. When cats meow, they are vocalizing the way we do: during exhalation.

But when the brain sends signals for the laryngeal muscles to expand and contract to vibrate the air, that's purring.

The Frequency of a Purr

The purr of domestic cats vibrates at 20-140 Hertz. How does that relate to why cats purr? Because that frequency of sound has therapeutic benefits.

Sound waves in that frequency range can help heal damaged muscles and ligaments. They can promote bone repair and strengthening. They can contribute to a reduction of inflammation and even tissue regeneration.

Are those benefits only for the purring cat? No. The therapeutic sound is a standard part of several kinds of injury treatment and rehabilitation in people. But the vibrations are made by a machine, not a furry companion.

Why Do Cats Purr?

No one knows for sure why cats purr. But the three most popular theories from zoologists involve:

  • Endorphins
  • Communication
  • Neural Oscillation

1. Endorphins

Endorphins are a collection of hormones that affect the nervous system in cats, humans, and many other animals. The biological function of endorphins is to inhibit the transmission of pain to the brain. Large releases or floods of endorphins can also cause euphoria.

Stress, injury, fear, and exhaustion are some of the triggers that release endorphins into the bloodstream. In people, endorphins can lead to laughter or a "high" feeling, which is the body's way of protecting itself against pain.

In cats, the release of endorphins can cause involuntary purring. In response to physical or emotional stress, such as going to the vet, purring eases the pain.

Does this mean that when you pat your cat, and he purrs, he's in pain? Of course not.

Dr. Kelly Morgan, DVM, an American veterinarian and clinical instructor, suggests equating purring to smiling. 

People will smile when they’re nervous, when they want something, and when they’re happy, so perhaps the purr can also be an appeasing gesture.

Dr. Kelly Morgan

Feelings of contentment (and in humans, happiness, and joy) can trick the brain into releasing endorphins and creating the sense that "all is good." The reason for this remains unclear, but anecdotal evidence is substantial.

2. Communication

The smiling analogy also illustrates the second popular theory about why cats purr: communication, which includes influence.

There's no doubt to anyone who lives with cats that our feline friends are master communicators.

Tail gestures are active signals to convey their mood. They only have to look at their empty dish a certain way or walk across your keyboard to let you know they want dinner.

3. Contentment and Attention

Purring is a simple way to communicate contentment or offer reassurance. Many cat owners report their feline seeking them out, making physical contact, and purring during bouts of crying or other emotional stress. It's as if the cat is communicating reassurance and camaraderie.

In cases like that, purring is voluntary. The cat seems to know that purring, those vibrations, will help calm you and reduce some of your emotional or physical discomforts.

Sometimes it seems that cats use purring to get or keep attention. They appear to know that most people find purring pleasant and they'll use it as a lure and reward for your company or attendance to their needs.

4. Kitten Communication

Purring for communication is a behavior they learn shortly after birth.

Kittens are born blind and deaf. It takes two weeks for them to open their eyes and develop a vision. Soon after, their ear canals will open, and they can hear.

During those critical early days, the most effective and efficient way for mama cat to reassure and comfort her babies is through physical contact and the vibrations of purring.

In turn, kittens learn to purr when they are 2-3 days old. At first, they purr while nursing. Some zoologists believe that early purring is linked to the way kittens knead their mother's belly to help stimulate milk flow.

The kittens knead, milk flows, they feel good, they purr, the mother's nervous system responds by relaxing, milk production increases, and kittens continue to be happy and fed. Purring might also be the kittens' way of saying "hey I'm here and everything's fine." After all, you can't meow when you're eating.

5. Conflict

Cats will also purr during a conflict with another cat. Purring is a way for a cat to say "We're cool. No need to attack each other."

This is a typical behavior when an elderly cat is near a younger, more aggressive cat. The older feline will purr as if to say "I'm old and not looking for trouble." It's effective communication because seldom will a younger cat show aggression toward a purring older one.

Pain is also a reason why cats purr. This helps to explain why they purr while giving birth or undergoing medical procedures without sedation.

6. Neural Oscillation

The third theory to explain why cats purr involves another involuntary body function. Neural oscillation is an intricate process that results in brain signals managing some of the body's involuntary actions. Examples include making the heartbeat, muscle coordination for motions like walking, and the REM stage of sleep.

Some zoologists say a neural oscillation triggers purring.

This could be true. Yet it doesn't explain why cats purr.

When Cat Purring Isn't Good

If your kitty is purring but doesn't want to be touched, or purring while thrashing her tail, she could be in serious physical discomfort or medical distress.

Don't fall into the trap of thinking that if she's purring, the situation can't be all bad. The purrs are probably a combination of an involuntary response to pain or discomfort and communication about the same.

If the purring and other signs of discomfort persist for more than 15-20 minutes, it's best to err on the side of caution. Gently put your cat in a secure carrier and take her to the vet for an examination.

You can also minimize stress-purring during emergencies such as extreme weather and evacuations buy protecting kitty in a soft-lined carrier. And make sure your emergency kit includes familiar items.

Summary: Know Your Cat

There's one question more important than why cats purr: why does your cat purr?

We've explored the popular theories about purring. But every cat has its own personality and physical attributes. One cat may be more emotionally needy than its sibling. Another cat could have a higher pain threshold than its cousin.

In the end, not all cats purr for the all the same reasons. Just like some people smile more than others and for different reasons.

Armed with the understanding that purring can be a physiological response to emotional and physical pain as well as a tool for communication, study your cat's purring patterns. With a deeper understanding of your cat's unique reasons for purring, your bond can become even stronger.

Do you know what makes your cat purr? Share your stories in the comments box below.

And, if there's anything you want to ask about cats, drop us a note. We love to hear from new and old cat friends.

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