Monday Medical: What is that thing on my cat's ear?

Today’s Monday Medical is by special request:
Amy over at Sebastian the Sensitive Soul asked if we’d write about that funny little flap at the base of a cat’s ear. What is it, and why is it there?

It was so cool to have someone suggest a topic, and loads of fun to research!

So here goes:

As many of you know, when we first adopted Maxwell we quickly discovered he was completely deaf. So the feline ear and how it functions has been of special interest to us. A cat’s ear is quite unlike the ones we humans are stuck with.

You may have noticed, for instance, that theirs swivel whereas ours don’t. Not only do they have a good 180 degrees of movement, each ear can move independently. Thirty-two different muscles power each ear. Impressive, yes?

The most prominent part of a cat’s ear – the erect part, distinguished and elegantly arched – is called the pinna. These pinnae are designed to draw sounds into the ear canal. Now those are some pretty fancy ‘dish antennae’!

Faraday's pinnae

The range of a cat’s hearing is much broader than most animals, almost triple the range of humans and twice what dogs can hear.

A cat’s hearing is especially acute at higher frequencies, which may have evolved in this manner because so many species in their food chain make sounds in that range.

According to Dr. Steven Bailey, cats have 10,000 more auditory nerves than us humans. They can resolve the difference between two sounds with great clarity: from 6 feet away, they can distinguish between sounds that are only about 3 inches apart.

And from 60 feet away, they can differentiate between sounds that are only a foot apart!


(Think your hearing is this acute? Try this at home: stand 6 feet away from someone holding 2 clothespins. Make sure they hold them only 3 inches away from each other. Close your eyes and see if you can tell which hand is “snapping” the clothespin – the one on the left or the one on the right. Nah, not even close! )

Now what about that little flap at the outer base of each pinna? Well, it’s known as a cutaneous margin pouch.

As for its function? Scientists aren’t entirely certain, but they suspect it plays a role in differentiating between various sound-waves. As highly engineered as these feline listening devices are, we don’t doubt it!

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Sources:

Dr. Steven Bailey of Exclusively Cats Veterinary Hospital, Waterford, MI
Vetbook
Consultations in Feline Internal Medicine, Volume 6 -, Volume 6,  John R. August
Wikipedia