Cat purring remains a mystery that we don't fully understand

Cats have captivated our attention for their wide range of vocalizations, from meows to screeches. However, it’s their mysterious purring that has been a subject of fascination and study for many years. 

Cats are not the only animals that purr, as once believed. Some wild cats, mongooses, hyenas, guinea pigs, and raccoons also purr.

Interestingly, purring and roaring are mutually exclusive. This means that cats that purr (such as mountain lions) can’t roar, while cats that roar (such as tigers) can’t purr. 

How do cats purr?

A new study led by Austrian voice scientist Christian T. Herbst at the University of Vienna is challenging long-standing beliefs surrounding the mechanics of cat purring. 

Contrary to previous understanding, the study reveals that the generation of cat purrs does not rely on cyclic muscle contractions – a perspective held by the scientific community for over fifty years.

“We propose that the ability to produce self-sustained oscillation at purring-like frequencies is facilitated by a special anatomical adaptation,” wrote the researchers.

Cat vocalizations

Cats produce various sounds, including meows and screeches. These sounds were not previously considered unique from a voice production standpoint as they originate in the cat’s larynx, or “voice box.” This mechanism is shared with humans and many other mammals. 

However, cat purrs were believed to be different. They were thought to be produced through continuous cyclic contractions and relaxations of muscles in the vocal folds in the larynx, which would require consistent neural input and control from the brain.

A new viewpoint 

The study led by Herbst introduces a different viewpoint. According to the findings, cyclic muscle contractions are not imperative for the production of cat purrs. 

Through controlled laboratory experiments, the researchers observed that the domestic cat larynx could yield low-pitched sounds characteristic of purring without the need for cyclical neural input or repetitive muscle contractions.

Unexpected findings 

These findings reveal an unexpected similarity between the sound production mechanism of cat purring and the human “creaky voice” or “vocal fry.” 

The data shows that cats can produce purring sounds at extraordinarily low frequencies (20-30 Hz), which is surprising considering their small size and weight.

Unique anatomical adaptation 

“Anatomical investigations revealed a unique ‘pad’ within the cats’ vocal folds that may explain how such a small animal, weighing only a few kilograms, can regularly produce sounds at those incredibly low frequencies (20-30 Hz, or cycles per second) – far below even than lowest bass sounds produced by human voices,” said Herbst.

While the study does not entirely debunk the older theory, it shows that our current understanding of cat purring is incomplete and further investigation is needed. 

The more we learn about the mechanisms and functions of purring, the better we can protect the well-being of our cats and accommodate their needs.

More about purring 

Some researchers believe that purring helps cats heal. The low frequency of purrs causes a series of related vibrations within their body, which can:

• Heal bones and wounds.
• Build muscle and repair tendons.
• Ease breathing.
• Reduce pain and swelling.

Kittens start to pur when they are a few days old during nursing, which could be a way of communicating relaxation and contentment to their mothers. Adult cats also purr when they feel safe and comfortable.

Cats may also purr during stressful or painful moments, like while visiting a vet or during illness. This is believed to release endorphins, which can relieve pain.

The study is published in the journal Current Biology.

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