Introduction
One of the most interesting behaviors exhibited by cats is the continued purring when sick or injured. Though we associate purring with happiness and contentment, cats continue to purr even when unwell as a survival mechanism. In this article, we will explore the reasons behind purring in sick cats, the benefits cats receive from purring when ill, and what purring behavior can tell us about a cat’s health.
Though it may seem counterintuitive, there are several evolutionary advantages to purring even when a cat is not feeling its best. The rhythmic vibrations of purring have been shown to promote healing, alleviate pain, and elicit caregiving from humans. Even in distress, purring allows cats to self-soothe, communicate with humans, and promote recovery from illness or injury through its physical therapeutic effects. By understanding why cats purr when sick or stressed, we gain greater appreciation for the remarkable adaptabilities of our feline companions.
Purring as a Healing Mechanism
One of the most fascinating potential benefits of a cat’s purr is its use as a healing mechanism. Research has shown that the vibrations produced during purring, which range from 25-150 Hertz, can provide therapeutic effects for cats and humans alike. When an injured or unwell cat purrs, the vibrations may help reduce swelling, relieve pain, and promote healing by stimulating bone growth and tissue regeneration (Source). The rhythmic vibrations also increase oxygenation as the cat takes deeper breaths while purring. This improved oxygen flow aids healing and recovery.
For humans, a cat’s purr has been associated with reduced stress, lower blood pressure, and increased healing and relaxation. The frequencies transmitted through a cat’s body while purring fall within the range that can promote tissue regeneration in humans. So when a cat purrs nearby, the vibrations may transmit these healing effects to their human companion as well (Source). While more research is still needed, a cat’s soothing purr certainly has the potential to provide therapeutic value for both cats and the people who love them.
Purring as a Calming Signal
A cat’s purr can serve as a calming signal that communicates to other animals that the cat is not a threat. When cats purr in the presence of other cats, humans, or even predators, it can help reduce stress and aggression in those around them. The rhythmic vibrational sound patterns of purring, especially between 25 and 50 Hertz, has a tranquilizing effect on the nervous systems of other animals. Studies show that continuous exposure to a cat’s purr causes a decrease in blood pressure, heart rate, anxiety, and other physiological indicators of stress or nervousness (Cat Purring Has To Be The Most Relaxing Sound Ever).
This calming influence allows cats to more peacefully co-exist and interact with humans and other animals. Kittens will often purr when feeding from their mother to stimulate milk production while also alleviating any stress. Adult cats continue this behavior when surrounded by potential threats as a friendly signal of reassurance that they are not going to cause harm. So next time your cat cuddles up on your lap and starts purring, know that it is engaging in active stress and anxiety reduction for both of you.
Purring and Self-Comfort
Purring releases endorphins in cats that provide pain relief and improve their overall sense of wellbeing (https://metro.co.uk/2016/03/20/is-your-cat-inappropriately-purring-heres-what-it-could-mean-5763624/). This self-soothing effect of purring is similar to when humans hum or sing to make themselves feel better. The rhythmic vibration of purring has a therapeutic quality that cats seem to instinctively understand.
Purring can be a way for cats to calm themselves down, especially when they are stressed, anxious, or in pain. The act of purring helps release endorphins that relieve discomfort and lower stress levels. Essentially, cats purr to soothe themselves in the same way that we might hum or listen to calming music (https://www.wired.com/2015/05/why-do-cats-purr/).
So when your cat purrs for no apparent reason or continues purring even when clearly injured or ill, it is likely an attempt to self-soothe and make themselves feel better through the release of endorphins. The purr provides a source of internal comfort.
Purring to Elicit Caregiving
One of the key reasons cats purr is to elicit a caregiving response in other beings, including humans. A cat’s purr sends neurological signals that trigger nurturing instincts in other cats and animals. Research shows that a cat’s purr, when directed at a human,
can actually cause a release of oxytocin, the “cuddle hormone”, in humans. This encourages us to be more caring, patient, and affectionate with the purring cat.
Kittens purr frequently to prompt their mothers to nurse, groom, and care for them. Adult cats may increase purring around humans or other cats when sick, injured, or distressed to elicit greater care and attention. The pitch and urgency of “caregiving purrs” is often higher and more insistent than contented purrs. So next time your cat purrs loudly while staring at you, it may just be their way of asking for some special care and comfort!
Evolutionary Benefits
Purring likely provided an evolutionary advantage to sick or injured cats. Cats who purred more frequently while ill or hurt were more likely to survive and fully recover, compared to cats who purred less often. This allowed purring cats to live longer, reproduce, and pass on the purring trait to future generations.
One theory suggests purring evolved as a healing mechanism for cats (Scientific American). The vibrational frequencies produced while purring fall within a range that can improve bone density and promote healing. Purring may physically help cats recover from illness or injury by stimulating this self-healing process.
Another view is that purring provides a survival advantage by eliciting caregiving from humans (Catevolution). When cats purr, they appear content, less threatening, and trigger a caregiving response in people. This makes humans more likely to feed, protect, and aid purring cats when sick or hurt. In this way, purring cats secured more resources and better chances of survival.
Unique Feline Anatomy
Cats have a unique larynx and diaphragm that allows them to purr continuously, even while breathing. This differs from other big cats like lions and tigers that cannot purr while inhaling or exhaling air (1).
A house cat’s larynx contains an ossified hyoid bone that vibrates when air passes through the larynx, creating a purring noise. Special sinewy tissue connects the hyoid bone to the larynx muscles, allowing it to continuously vibrate as the cat breathes. The diaphragm has a special tendon that also oscillates as air moves in and out, contributing to the purr (2).
Other big cats like lions, leopards, and tigers have a similar larynx anatomy, but their hyoid bone is not completely ossified and lacks the specialized sinewy attachments. This prevents continuous vibration as they breathe. Their purr is therefore limited to the exhale phase when breathing out (1).
This unique larynx and diaphragm adaptation likely evolved in small cats as a means of continuous communication and healing through purring. Their ability to purr while breathing in and out allows house cats to maintain this soothing vibration even when engaged in other activities.
(1) https://www.loc.gov/item/why-and-how-do-cats-purr/
(2) https://www.science.org/content/article/how-do-cats-purr-new-finding-challenges-long-held-assumptions
Purring in Other Cat Species
While domestic cats are well known for their purring abilities, they are not the only felines that can produce this soothing vibrational sound. Many other small wild cat species, such as cheetahs, ocelots, and margays, can also purr. In contrast to their larger relatives like lions and tigers, these smaller cats have an anatomy that allows them to both inhale and exhale while purring. Their hyoid bones contain ossified cartilage that enables vocal fold vibration on both inhalation and exhalation [1].
Unlike domestic cats, larger wild cats like lions and leopards cannot purr continuously. They produce a raspy exhaling “whirr” or “chuff” sound on exhalation but lack the special hyoid bone structure to purr while inhaling. This anatomical difference also explains why larger wild cats can produce a full-throated roar using their larynx cartilage, while domestic cats are limited to meows and purrs [2].
So while your pet cat’s soothing purr may be reminiscent of the big cats you see on wildlife documentaries, only the small wildcats actually share this unique vocalization trait. Next time your feline friend is vibrating a comforting purr, remember it is an ability passed down from their ancient wild ancestors.
Purring Across Life Stages
A cat’s tendency to purr changes over the course of its life. Kittens are known to purr frequently as a means of signaling to their mother that they are hungry or in need of care and comfort. The vibrations created by a kitten’s purr serve as a cue to the mother to nurse or groom the kitten. According to a study by McComb et al., hungry kittens purr at a near-constant rate while nursing to encourage the mother to keep producing milk.
In contrast, senior cats often purr more frequently as well. Older cats dealing with age-related health issues may purr to self-soothe and boost their mood. The calming effects of purring can help senior cats deal with anxiety, chronic pain, cognitive decline, and separation from family members (Jones, 2018). For example, an elderly cat may purr loudly at night while wandering around a dark house, using purring to comfort themselves while navigating the environment. Purring may also elicit caregiving from human owners who are attuned to what the vocalization signals.
Conclusion
Cats are vocal creatures, using a range of sounds to communicate with each other and their human caretakers—but perhaps no vocalization is more endearing than the deep rumble of a cat’s purr. When our sick cats purr, it opens our hearts even while it puzzles our minds. Why would an unwell cat purr, when purring takes effort and energy?
As it turns out, there are several key reasons sick cats continue to purr.
Purring is a self-soothing mechanism for cats, releasing endorphins that help relieve pain and calm them during stress. Purring may also promote healing by helping regulate breathing, increase bone density, and stimulate healing muscles and joints.
Purring serves as a calming signal to other cats and people, expressing friendliness, contentment, and safety. This helps ease social interactions.
Purring provides cats comfort and reassurance. The rhythmic vibration is both psychologically and physiologically calming for cats.
Purring elicits caregiving from human caretakers. Something about that sweet rumble compels us to show affection, petting and comforting our cats.
So while a sick cat’s purr may seem paradoxical, it actually serves several important purposes for feline health and wellbeing. Understanding why cats purr, in sickness and in health, gives us greater insight into the fascinating behavior of our feline companions.