Most of us can agree that cats are pretty adorable. Otherwise, there wouldn't be an entire genre of internet memes dedicated to them, but cat lovers will still debate about which feline features are the cutest. Is it their paw pads (which you might affectionately dub toe beans) or their tiny delicate whiskers? Do the wrinkles of a sphynx reign supreme? For many, it's all about the ears.
Anatomically speaking, cat ears aren't all that different from human ears in the way they function, but cats actually have very keen auditory senses. Their triangle-shaped ears are designed to hear much more than humans, and almost every piece of your cat's anatomy works towards this ultimate goal — everything except your cat's cutaneous marginal pouch.
You might have noticed a little slit or pocket at the base of your cat's external ear. This mysterious (and utterly adorable) pocket is called a cutaneous marginal pouch or, more colloquially, Henry's pocket. Though the actual function of Henry's pockets are unknown, experts do have some theories about their ultimate purpose.
How cats use their ears
Like humans, cats use their ears for hearing and balance. The main difference is that cats can hear far higher frequencies than both humans and canines. So, for example, your cat definitely can hear a dog whistle and beyond. Though they're a bit less adept at hearing low end frequencies, cats can distinguish differences in sound as little as one-tenth of a tone (for reference, most music uses half tones and quarter tones). This helps them identify the size and distance of their prey or pinpoint the location of one of their kittens should it wander beyond eyesight — and they do this with razor sharp accuracy.
Cats can hear sounds that are four or five times farther away than those humans can hear. They can also target a sound's location in six one-hundredths of a second from a distance of up to three feet. Remember, your domestic cat might like napping on your lap, but it's a natural-born hunter.
The anatomy of a cat ear
Cat ears (and human ears) have three different sections that work together to amplify and process sound as well as regulate balance. This includes:
- The inner ear
- The middle ear
- The outer ear
As the old adage goes, a cat always lands on its feet. Part of this has to do with their highly developed inner ears, which give them excellent agility and a sharp sense of balance. The inner is composed of the cochlea, which helps your cat hear, and the vestibular system, which is responsible for balance.
The middle ear consists of two muscles, the eustachian tube, the oval window, the eardrum, and an air-filled chamber with three bones called the hammer, anvil, and stirrup. In humans, these are the three smallest bones in the entire body.
The outer ear is mostly composed of the pinna, the fleshy cartilage you see that may or may not have fur, and the ear canal. The pinna's unique shape catches and amplifies sound as it's funneled into the eardrum. Unlike humans, cats can independently move their pinnae, allowing them to target specific sounds. They also have a deeper ear canal which does a better job at carrying sound, but it also leaves them more susceptible to inflammation and ear infections.
The purpose of Henry’s pockets
Henry's pockets (or cutaneous marginal pouches) are located on your cat's outer ear, but other species like bats, weasels, and some breeds of dogs also have them. The true purpose is unknown, but experts have a couple theories. First, they may help your cat more accurately locate prey and predators and enhance sound, allowing for greater efficiency when your cat angles its ears. They also might make ears more flexible, allowing cats to express their emotions (think: anger, discomfort, fear, and even playfulness) through the position of their ears.
In truth, Henry's pockets might actually have no function or a function that hasn't yet been discovered. As cats evolve, their bodies change to maximize survival. Anything is possible.