Cats and Science
Share this image

Into the Gene Pool: Why a Lot of White Cats Are Deaf

"Star Trek" is the reason white cats are deaf. What does that mean? Well, ion balance must be maintained! Let me explain.

Lisa Richman  |  Mar 4th 2015


Wait. This is a cat site, right? So what’s with the whole “Beam me up, Scotty” stuff anyway?

Aside from the fact that I’m a long-time sci-fi groupie and lifetime NASA brat, I totally blame this one on my cat. The nice one. The one who, on the day we brought him home from the adoption event, we discovered was absolutely, profoundly, utterly deaf.

Maxwell was diagnosed with gingivostomatitis as a kitten.

Since that day, I’ve learned a lot about deaf cats. I’ve made it my business to understand the mechanics of deafness, and to learn what I can do to make my cat’s life safer and more comfortable. Maxwell made it easy. He is such a mild-mannered, sweet-tempered boy (who doesn’t even mind his fur being groomed by my husband’s Shop-Vac).

Because of Max, I’ve had a lot of people reach out and ask hearing-related questions. I’ve had some real interesting ones, such as, “Why are a lot of white cats deaf?”

Good question.

Smiling kitty by Shutterstock.

Are all white cats deaf? No, it varies from 17 percent to 80 percent, based on eye color.

Before I go all sci-fi on you and start throwing around Doctor Who references, let’s take a peek at a little science fact. I’ll make it painless.

1. Eight different genes determine what a cat’s fur will look like

Hold on. We’re talking about deafness, not the color of a cat’s fur. Correct. But, believe it or not, it begins here. So, back to these genes. Some of them are more basic, while others are what you’d call modifiers. An example of a basic gene would be the black gene. Another would be the orange gene.

2. The white gene isn’t a color gene but a masking gene

If a cat has this gene turned on, then the gene’s basically overwriting any color gene your cat has. And if the color’s erased, what you’re left with — is white. This gene, along with its “sister gene” the spotting gene, are responsible for 99 percent of the white fur you see on cats.

This Literary Kitty can thank the Spotting Gene for his tidy white gloves. Literary Kitty by Shutterstock

Let’s begin with the spotting gene. It has three basic settings: low, medium, and supercharged. If the setting’s on low, it’s called a gloving gene. Like you’ve probably guessed from its name, it “puts gloves” on a cat. You’ve seen them: Those cool white paw markings on some Ragdolls, Himalayans — and of course, the Snowshoe.

If the setting’s on medium, that’s when it’s called the spotting gene. That’s what can give a cat that classic tuxedo look with a white blaze along the nose and that elegant white bib down the chest. The S gene is responsible for other styles of black-and-white coat patterns, too, like the ones you see in cow cats.

Cow cat? Um, no. Cute costume, though. Would your cat let you dress it up? Mine wouldn’t! Cat dressed as a cow by Shutterstock

Often, a cat we think of as a white cat really isn’t. At least, not genetically speaking. If the spotting gene setting’s on high, then you have a white cat. Or at least it looks like you have a white cat. But if there’s even one colored hair anywhere on a kitty’s body, that cat isn’t truly white. This kitty basically has one big white spot all over his body.

A truly white cat will have the white gene. And as I mentioned earlier, the white gene is a masking gene. And that truly does mask all color on a cat. Everywhere.

Enough already. Bring on the Tardis. Warp speed, please!

Alrighty then! How’s this?

Because the white masking gene is responsible for masking all color everywhere, that means pigment is masked or blocked in the eyes and ears, too.

(By the way, masking pigment in the eyes is what causes them to be blue. You can read about why they’re blue rather than, say, albino pink, in my article “Did You Know Siamese Cats’ Eyes Explain Why the Sky Is Blue?“)

So, what makes a white cat with the W — or white masking gene — deaf?

White kitten by Shutterstock

Star Trek.

Um. Come again?

Star Trek is the reason white cats are deaf

Okay, well, maybe I’m stretching the truth just a teensy bit.

Here’s what’s going on: There is a spiral-shaped cavity in the inner ear called the cochlea. This is where sound waves are converted to electrical signals and sent to the brain for processing. In order for those electrical signals to be transmitted upstream to the brain, ion balance needs to be maintained.

(Sounds like some kind of warp drive, doesn’t it? Like I said, Star Trek. I rest my case.)

I have no idea what ion balance is, and if you figure it out please let me know, because I’m weird like that and love to get my geek on. Bottom line here is, the thing responsible for maintaining this mysterious ion balance is a thin layer of melanin pigment called melanocytes, and these cells coats the inside of the cochlea.

Can you see where we’re going with this? If the white masking gene blocks the production of all pigment in a cat’s body, then that melanin isn’t going to be there. No melanin means no ion balance. No ion balance means no sound transmission. No sound transmission means deafness.

So there you have it: Star Trek — the reason white cats are deaf.

But what about odd-eyed cats?

There are occasions where the spotting gene does invade the cochlea and prevent the melanin layer from developing. But this is fairly uncommon. In fact, 60 percent to 70 percent of all odd-eyed cats hear just fine, thank you.

odd-eyed-cat-162250958

Odd-eyed cat photo by Shutterstock

Any apparent deafness must be attributed to the fact that your cat is, well, ignoring you. Shocking, I know.

Oh, by the way, our Maxwell’s deafness isn’t caused by that. He’s got plenty of melanin in his ears. His deafness is from a birth defect: He has no eardrum.

White cats also are not albino cats. Albino cats exist, but they have the albino gene and can usually be identified by their pink pigmented eyes.

And … true albino cats are not deaf. Go figure.

Read more about cats and genes on Catster:

About Lisa Richman: Writer, director, pilot, foodie, cat person. When she’s not on set, this director of film and video can usually be found taking photos of cats (and food) with her trusty Nikon, or cruising aloft at 3,000 feet. She’s cat mom to an opinionated Tonkinese, a hearing-impaired Siamese, and a feline fashionista. She’s also the owner of a recently launched food blog, and the Cat Writer’s 2014 Entertainment Blog, A Tonk’s Tail.