ASK A SCIENTIST
Question: Why do cats purr?
Answer: Cats make many vocalizations through the meows of a greeting to begging for attention or food or the defensive sound of hissing when they encounter a threat. Purring is probably the most common of sounds used by cats, used to express apparent contentment when you pet them.
There are many possible reasons for cats' purrs and there are different types of purrs. Amazingly, scientists haven't agreed upon the real reasons and origins of purring. There are even different ideas on how cats purr. Some believe it could be the vibrating of vocal cords, diaphragm or blood vessels, and may or may not involve the intercostal (rib) muscles. Whew!
The possible reasons for purring might be discerned from the situations in which cats purr. Cats purr when greeting someone, sitting in on someone's lap, being petted, or laying in the sun. These are situations where the cat is apparently comfortable and the sound is probably a sign of satisfaction.
Between a kitten and its mother, purring is likely a form of bonding and reassurance. Mother cats will purr to their kittens. Kittens are even able to purr while nursing whereas they can't meow at the same time as nursing. According to the book, The Cat's Mind, veterinarian Bruce Fogle theorizes that the ability of kittens to purr while nursing may be the origin of purring in general.
Some cats will use a loud higher pitched purr in place of, or in addition to, meowing when begging for food or attention. Most intriguing of all is that many cats will purr when in pain, injured, or giving birth. Some think that the vibration of purring helps to relieve pain. It is certainly possible. Some even believe that purring heals cats when injured and there are reports that the vibration frequency of purrs helps to promote bone growth. If purring acts as a means of stress or pain relief, then it is likely that purring can speed up the healing processes of a cat's body. The same concept can be applied to humans. For example, when someone is sick or injured interaction with animals or pets has been proven to relieve stress and speed up the recovery process.
So, if you have a cat, pay attention to the sounds it makes. It will help in figuring out how to take good care of it. Then, perhaps you will be able to figure out why it purrs.
Ask a Scientist appears Thursdays. Questions are answered by faculty at Binghamton University. Teachers in the greater Binghamton area who wish to participate in the program are asked to write to Ask A Scientist, c/o Binghamton University, Office of Communications and Marketing, PO Box 6000, Binghamton, NY 13902-6000 or e-mail firstname.lastname@example.org. Check out the Ask a Scientist Web site at askascientist.binghamton.edu. To submit a question, download the submission form(.pdf, 460kb).