Over time, evolution molded the anatomy of different animals, discarding unneeded features and perfecting others that aid in survival of a particular species. Cats have a curious anatomical feature – a little pouch-like pocket at the base of their ears that has a nifty name, but what is its function?
The Feline Ear
A cat's ears are designed to pick up the high pitched sounds made by their prey. Cats can rotate their ears 180 degrees and hear higher and lower frequencies than dogs. There is a fuzzy little pocket on the outer part of the ear that isn't commonly found in other animals, except the Fennec fox, bats and a few dog breeds. The scientific name for this small slit is cutaneous marginal pouch, but it's more commonly called Henry's pocket. It's nothing more than a fold of skin, but the purpose of Henry's pocket is as much of a mystery as the origin of its name. The design of the ear could provide some insight into the function of Henry's pocket, although the only thing scientists have right now are theories.
The overall makeup of the feline ear has three parts – the outer ear, middle ear and inner ear. When looking at the ear, the triangle-shaped part we see is the outer ear called the pinna, which funnels sound waves into the ear canal to the middle ear. Small bones then send vibrations to the inner ear. Henry's pocket is found on the outer part of the pinna at the base.
Three Theories
One theory is that the Henry's pocket may help kitties detect high pitched sounds, especially while hunting when it's common for the ear to be angled. The ability to accurately locate a sound is essential for a predator like the cat, who can pinpoint the specific direction and distance of a squeak or rustle to within 5 degrees. The hearing of cats is so keen they can discriminate even the slightest variation between sounds 3 feet away, and even determine the size of the animal making the noise. Being able to hear a wider range of sounds and differentiate between sounds gives felines a better chance of detecting prey, as well as predators they need to avoid.
Another theory is that the pocket helps enhance the detection of sounds. When a cat angles her ear, the pouch helps to make the action more efficient. Each ear has 32 muscles that allow a cat to move them independently. This makes it possible for a kitty to move her body in one direction while pointing her ear in another direction.
A third theory is that those cute little slits help dogs with a Henry's pocket flatten their ears, but cats don't fold their ears like canines do. However, the slits might add a little more flexibility to the ears and make it easier for cats to express their discomfort, fear, anger or contentment by the position of their ears. A growling or hissing cat folds her ears back against her head to indicate what she's feeling. The ears are pulled back when listening to a sound behind her, and a yawn causes the ears to fold back.
Of course, it's always possible that the slit has absolutely no function whatsoever, but that's probably not the case. Survival is dependent on efficient adaptation, so there likely is a reason for the pocket that hasn't yet been discovered.
What is certain about Henry's pocket is it's a breeding ground for ear mites; ticks also love to hang out in it. The area is dark and can be moist – an inviting place for fungal infections and bacteria. So it's important to keep an eye open for any uninvited pests taking up residence in your cat's cutaneous marginal pouch.
