February 19, 2025, 10:18 am | Read time: 4 minutes

You may have noticed it before: The small “pocket” on the outside of a cat’s ear. Its exact function is still unclear – but there are a few theories. Biologist and PETBOOK editor Saskia Schneider explains what they are and why you should pay special attention to the little fold.

Cat’s Ears Hear Mainly in the High-Frequency Range

Hearing is one of the most important senses for cats. Their ears are perfectly designed to precisely locate sounds and thus reliably find their prey – even if they cannot see it. To do this, cats have 32 muscles in their ears – almost twice as many as most dogs. They allow cats to move their ears independently of each other. This means that cats have very good spatial hearing.

Cats are also at the forefront when it comes to hearing frequency. They can hear a whole octave higher than dogs. They, therefore, perceive sounds in the high-frequency range particularly well – this is partly due to their specialization in certain prey animals. And this is where Henry’s pocket comes into play.¹

The True Function of Henry’s Pocket Is Still Unclear

Although the exact function is still unclear, one of the most common theories is that the fold of skin helps with the perception of high-frequency sounds by attenuating lower sounds, especially when the ear is angled, which is common for a predator when hunting. However, there is no scientifically proven evidence for this yet.

Another theory about Henry’s pocket is that the fold of skin allows the ear more room to move. When cats try to locate their prey, they turn their ears. These are so flexible that they allow the cat to walk in one direction and listen in the other. The pocket could ensure that the ears give way even more at this point and can, therefore, be turned or flattened even further. But there are no studies to prove this either.²

It is also possible that Henry’s pocket no longer has any function at all. Perhaps it is a relic of feline ancestors that no longer has any significance today. However, this is unlikely, as other animal species with excellent hearing also have a Henry’s pocket on their ear. These include weasels, bats, and some dog breeds.

Who Is This Henry?

But who was this Henry, and what did he have to do with cat ears? This, too, is still a mystery to science. What we do know is that the name first appeared in an archive from 1971. But where it came from is unclear. One theory is that the small fold of skin was named after Joseph Henry. The mathematician and natural philosopher studied electromagnetism and sound waves and made some remarkable discoveries in these fields. But this is also pure speculation.^{3, 4}

Why You Should Keep an Eye on Henry’s Pocket

Although we still don’t know the exact function of Henry’s pocket, owners should keep a close eye on it. This is because what we do know is that parasites such as ticks or fleas prefer to nest there and are, therefore, easily overlooked. So the next time you check your pet for unpleasant things from outside, you should pay particular attention to the small fold of skin.

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Conclusion

The function of Henry’s pocket on the cat’s ear is unclear. The most likely theory so far is that the small fold of skin improves hearing at high frequencies, as it is mainly found in mammals that hear particularly well in this range. Incidentally, the internet has its own theory about Henry’s pocket. It is believed that it gives the cat an “extra cute look” and helps the animal to ignore its humans.