PET FRIENDLY: Why Cats Purr?


A significant portion of my business involves caring for the needs of cats, who are generally more challenging to “read” than my canine clients. Perhaps because of this reality, I have written more in this Pet Friendly column about dog behaviors and care than about those of cats.

Since cats are North Americans' most popular pets (73 million cats vs. 63 million dogs) and live in 30 percent of our households, it’s time to talk more about them. From my direct observations of cats (and aren’t they fun to watch!) and research on them, I’ve uncovered some interesting “facts.” According to

  • Cats make about 100 different sounds, while dogs only make about 10.
  • Most wild cats (bobcats, mountain lions) and related species (guinea pigs and raccoons) purr, but big cats that roar (lions and tigers) don’t purr due to differences in their larynxes.

Most veterinarians agree on the mechanics of purring: cats purr through intermittent contracting of muscles in their larynx and diaphragm to rapidly open and close the airway in their throat.  Expert consensus breaks down, however, when we ask why cats purr. 

Why Cats Purr

Leslie Lyons, an assistant professor at the School of Veterinary Medicine at the University of California, Davis, offers these opinions based on recent research:

  • As cats have evolved, purring has likely offered selective advantages as a communication tool. In pet cats, purring often accompanies nursing of kittens or social interaction – such as stroking or feeding – with their owners. And small pet cats don’t need to roar to mark and protect their territory and food from other cats like a lion or tiger does.

  • Cats also may purr when ill or under duress, such as during a visit to a vet or when recovering from an injury, when it appears to have a self-calming or recuperative effect. Scientists have documented that measured sound frequencies in a cat’s purring (25 to 150 Hz) can improve its bone density and promote healing of muscles. Cats conserve energy through long periods of rest and sleep, leading to the hypothesis that purring is a low-energy means of stimulating healthy bones and muscles.

One of the more interesting observations about purring comes from Kelly Morgan, DVM, clinical instructor at the Chicago Center for Veterinary Medicine of the University of Illinois at Urbana-Champaign: “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,” adding that this is “purely speculation.”

Karen McComb, PhD, who recently completed research on cats at the University of Sussex in Brighton, U.K., notes the ability of cats to add a vocalization to their basic 25 Hz purr to generate a more urgent and persuasive purr/meow. This sound appears to be most prevalent in quiet households where cats have a close relationship with their owners.

Rebecca Johnson, PhD, RN, FAAN, director of the Research Center for Human Animal Interaction, notes that we associate purring with calm and contentment.  She reports that studies of human/pet interactions suggest cats do a better job of lowering our own stress and blood pressure than do many other pets, and speculates that purring may be part of that effect.  So enjoy and reward your cat’s purring – it serves you both well!

Chris Bates is the founder of Top Choice Pet Care LLC (, which provides affordable, loving and reliable dog walking, pet sitting and other pet services to the Bristow, Gainesville, Haymarket, Manassas and Nokesville communities.  A farmer’s son, life-long animal lover and pet owner, Chris is a Certified Professional Pet Sitter (CPPS) through Pet Sitters International and is PetSaver™ trained in pet first aid and CPR.


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