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Why Cats Purr

No one really knows exactly why cats purr.  It could be for social reasons —  to get the attention of their human or to create a bond with their offspring or their mother. Research suggests that purring also has restorative properties for healing and reducing stress.  Scientists have proposed that when a cat purrs while in distress, pain, or giving birth, they are purring to trigger the brain to release pain killing hormones. This may be related to healing.  Some scientists say that cats might even purr to manipulate their humans or their environment.

Another reason for the evolution of a cat’s purr starts at birth.  Did you know that kittens are born blind and deaf?  They rely on the sound and vibration of their mother’s purr.   At two days after birth, a kitten can purr.  This evolutionary trait could be a method for kitty mama and kittens to communicate, and locate each other.

We all know that it’s natural for a cat to do what a cat does best – to get something they want.  Call it the power of  Purr-suasion, if you will.  According to a study at the University of Sussex, cats will purr to gain food, attention, or affection.  This behavior mainly happens with indoor cats that have a close relationship with their human.  Purring, coupled with a high-pitched “purr-whine” can get their human to pretty much give into whatever the cat wants.

Admit it. You have done this when under the powerful pull of the feline purrsuasion. One study suggests that the high-pitched purr is very close to the high-pitched whine of a child, and makes it almost irresistible for owners not to investigate why the cat is making the sound.  I don’t know about this theory because I will run from the sound of  a shrieking child.  However, if I were to really be objective about this, I have to admit that when my kitties cry or whine I do get up and attend to their feline needs.

Karen McComb, PhD headed a study to explore the unique characteristics of these insistent purrs after wondering why her own cat could be “so annoying.”  In the study, recordings of 10 cats’ purrs revealed that cats sometimes develop a “twist on purring.”  Cats can add a vocalization into the mix to solicit responses from humans.  McComb’s team suggests that cats may have learned how to tap into a mammalian response for nurturing offspring by embedding a cry within a call that’s normally associated with contentment.

Added to the basic 25 Hz purr is an overlay of a high-frequency cry-meow that humans perceive as somewhat obnoxious.  Cats apparently learn to do this to get people to feed them sooner.

 

Purring is also associated with being content around others.  One study suggests that purring can be an attempt to be friendly to other cats, to other people, or to signal a specific intent.  For example, when a cat is being petted, asking for food, or even purring at the scary veterinarian’s office, purring could be a way to communicate ‘friendship’.  This study suggests that purring encourages humans to continue petting the cat, giving him or her attention, receiving food, or in the case of the veterinarian or an injury, to not hurt the cat.  In essence, the cat is stating that he or she is not a threat by purring.

 

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Feline Fact: Cats actually have a range for their purring, similar to how humans hum in different pitches.   A cat’s purring frequency ranges between 25 and 150 Hertz

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The Healing Properties of a Purr

Scientists have discovered that purring is a “natural healing mechanism.”  They have discovered that  wounded cats (both wild and semi-domestic) purr because it helps their bones and organs to heal.  Fascinatingly, exposure to similar sound frequencies has been shown to improve bone density in humans!  Scientists have also learned that cats release endorphins while purring.  Endorphins are a natural analgesic that assists to reduce pain during the healing process.

 

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Old wives’ tales usually have a grain of truth behind them, and most people have heard of  a cat’s “nine lives.” There is also an old veterinary adage still repeated in veterinary schools which states, “If you put a cat and a bunch of broken bones in the same room, the bones will heal.”  Any veterinary orthopedic surgeon will tell you how relatively easy it is to mend broken cat bones compared with dog bones which take much more effort to fix, and  take longer to heal. ~ The Felid Purr: A bio-mechanical healing mechanism

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Veterinary orthopedic surgeons have observed how relatively easy it is to mend broken cat bones, as compared with dogs.  In a study of “High Rise Syndrome” found in the Journal of the American Veterinary Medical Association, Dr. Whitney and Dr. Mehlhaff documented 132 cases of cats plummeting from high-rise apartments, with the average fall being 5.5 storeys (55 feet). The record height for survival was 45 storeys.  Ninety percent of the 132 cats studied survived even though some had severe injuries.  There is also literature that suggests that domestic cats are in general less prone to postoperative complications following elective surgeries.

But are purrs to thank for this healing? Researchers believe that self-healing is the survival mechanism behind the purr, specifically during times of pain, injury and distress.  There is extensive documentation that suggests that low frequencies, at low intensity, are therapeutic.  These frequencies can aid bone growth, fracture healing, pain relief, tendon and muscle strength and repair, joint mobility, the reduction of swelling, and the relief of dyspnea, or breathlessness.

 

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 Purring really cannot be considered a true vocalization, as the purr is produced under differing emotions or physiological states.

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Researcher Elizabeth von Muggenthaler of the Fauna Communications Research Institute in North Carolina (FCRI), a specialist in the field of bioacoustics, put it all together.  Bioacoustics is the study of the frequency, pitch, loudness, and duration of animal sounds as it relates to the animal’s behavior.  Based on her research, she proposes that nature has endowed all kinds of felines with an evolutionary healing advantage in the simple act of purring.

Remember that purring takes energy and cats purr not only when all is well, but also when the cat is giving birth, hurt or just scared. There has to be a very good reason for the energy expenditure to produce purring, especially when the cat is physically stressed or ill.  It would have to be somehow involved in its survival. Muggenthaler set out to find how; you can read a summary of her study and results here.

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 I have witnessed a cat purring when in pain, when in stress, and even when dying.

After our beloved cat, Samantha, was diagnosed with terminal cancer I learned about the healing power of purrs.  A malignant mass in her chest cavity prevented her from breathing normally.  Every breath was labored, but I noticed that she was purring constantly.  I had no idea at the time that she was purring to both heal and self soothe.

Samantha purred every time she was at the vet with me.  I knew she was not  purring because she was “happy”. She was self soothing.

This is a recording of my beloved cat, Samantha, purring while she was very sick with cancer at the end of our time together.  Even minutes before she passed away here at home with me, she was purring this loudly.

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Solving The Cat’s Purr Mystery using Accelerometers by Elizabeth von Muggenthaler and Bill Wright http://www.acoustics.asn.au/joomla/australian-acoustics-journal-august-2003.html http://www.bksv.com/NewsEvents/Waves/OtherArticles/TheCatsPurrMystery.aspx EverydayMysteries.com Why and How Cats Purr? http://www.loc.gov http://www.scientificamerican.com/article.cfm?id=why-do-cats-purr Foster, Dr.; Smith, Dr.. “Purring in Cats”. Pet Education.com. Retrieved 2011-04-10. http://www.loc.gov/rr/scitech/mysteries/catspurr.html Holton, Cara and Pires, Jackie. Purring in the Domestic Cat. Fall 2011, academic.reed.edu http://www.why-do-cats-purr.com/ Leyhausen, Paul. in Cat Behavior: The Predatory and Social Behavior of Domestic and Wild Cats, translated by Barbara A. Tonkin. New York: Garland STPM Press, c1979. http://www.leaflady.org/purr.htm Minard, Anne. Cats Use “Irresistible” Purr-Whine to Get Their Way. National Geographic News. July 13, 2009 http://www.animalvoice.com/catpurrP.htm Journal of the American Veterinary Medical Association; Healing and the cat’s purr – Fauna Communications Research Institute http://www.livescience.com/5556-cats-control-humans-study-finds.html Muggenthaler, Elizabeth Von. Felid Purr: A Healing Mechanism. 142nd Annual Acoustical Society of America, American Institute of Physics. 2001. http://news.bbc.co.uk/2/hi/8147566.stm http://news.nationalgeographic.com/news/2009/07/090713-cats-purr-whine.html