Why do some cats have extra toes or polydactyly?
Toe beans are arguably the cutest part of the cat. If you agree, then you probably find cats with extra toes extra cute.
But why do some cats have an excess of toes? What causes them to form? Are extra toes a sign that a cat is inbred? Is this condition very rare? Is it dangerous for a cat to have extra toes?
We’ll answer all of these questions (and more) in this post.
Polydactyly – the science-y term for extra toes
You can call them mitten-foot cats, snowshoe cats, thumb cats, six-fingered cats, conch cats, and, if you’re from Cardigan in Wales, Cardi-cats.
But the real word to describe cats who have extra toes is “polydactyl.” Add a “y” at the end, and you have the word, “polydactyly,” which is the name for the condition of having extra toes.
Does that sound like Greek to you? Well, that’s because the word polydactyl is Greek. “Poly” means “many” and “daktulos” means digits, in other words, fingers or toes. Polydactyly literally means “many toes.”
How many is many? Many is any more than a cat’s usual toe count: four on each back paw, and five on each front paw for a total of 18 toes. Note that the five on the front includes the dew claw – the little extra toe on the side that doesn’t touch the ground.
Polydactyl cats can have as many as nine toes on a paw. It’s far more common for a cat to have all his extra toes on the front paws than the hind. In fact, it’s rare to find a cat with polydactyly on the hind paws only, and even rarer for a cat to have it on all four paws.
Note that the extra toes usually appear on the thumb side of the paw, but that they can form on either side and in the middle, too.
What causes cats to have extra toes?
I want to point out, first, that polydactyly is not just a cat thing. It’s known to occur in humans, dogs, horses, mice, cows, goats, sheep, springboks, and birds, too. But it’s far more common in cats than any other species.
The answer to the question about the cause of polydactyly is complicated, but starts with a gene called Sonic Hedgehog, named after the video game character (scientists might be sillier than we give them credit for).
This gene got its name when scientists first discovered a mutation in fruit flies that caused the flies to be covered in fine hairs, making them look like little hedgehogs.
The Sonic Hedgehog gene is similar to the fruit-fly gene, but applies to more complicated animals, like cats and humans. Sonic Hedgehog is the gene that tells an embryo how and where to grow fingers and toes.
The mutation that causes polydactyly is not in the Sonic Hedgehog protein. But far, far away on the DNA – so far, in fact, that it was a miracle that it was found at all – there is a kind of switch that regulates Sonic Hedgehog in the paw. The mutation that causes polydactyly in cats, humans, mice and other animals, is in that switch. When the switch isn’t working correctly, it causes the Sonic Hedgehog gene to grow toes where there shouldn’t be toes.
But polydactyly isn’t caused by just one single mutation. At last count, there were at least 13 known versions of the mutation in the Sonic Hedgehog switch. There could definitely be more.
Where did polydactyl cats come from?
Polydactyly is a genetic condition that is passed from parent cat to kitten. It’s dominant, which means that if a kitten gets just one polydactyly gene from one parent, the kitten will have extra toes. This is worth knowing because it means it’s easier for cats to pass this trait on to their babies. It also means that in certain cat populations the condition will be relatively common.
It is not a sign, however, that a cat is inbred. It’s just trait, like eye color, or fur color, that is passed on from mom or dad to their kittens.
Extra toes do show up more frequently in cats who live in certain places. Polydactyly in cats is more common on the East Coast of North America – both Canada and the United States – and in South West England and Wales.
The question – as yet, unanswered – is whether the Brits brought the cats to the U.S. (specifically Boston, where trade began), or vice versa.
We know that cats with extra toes were popular as ship’s cats. They were considered lucky charms, and some sailors believed that the extra toes made these cats better rodent hunters. And while we don’t know for sure where the first polydactyl cats originated, the information we do have suggests that ports that established trade with Boston suddenly developed their own populations of many-toed cats.
So, it’s likely that polydactyly in cats originated in New England, that the cats were welcomed onboard ships, but then took shore leave at the next port. Wherever they landed, they started their own polydactyl cat communities.
Why aren’t there large populations of polydactyl cats in other parts of Europe? Historians believe polydactyl cats might have been associated with witchcraft in other parts of the world. Rather than being celebrated, they were hunted and killed, and thus failed to establish elsewhere.
Is having extra toes harmful to cats?
There are absolutely no other health concerns associated with this particular genetic difference in cats. It is purely an aesthetic condition.
The extra toes vary from being fully functioning digits to small pieces of soft tissue that aren’t really attached to the bone. These looser toes might be more susceptible to injury. It’s also possible that a toe that isn’t fully formed will have a deformed nail bed with a tendency for the toenail to become ingrown.
And having extra claws does mean extra nail trims.
But there is nothing else to worry about with a polydactyl cat. One study of a 100 cats (mostly Maine Coons), compared polydactyls to non-polydactyls on a number of points, including their reproductive health, height, and tendency to have other deformities, and found no difference between the two groups.
The flip side of this question bears asking, too. Does having extra toes confer any benefits to a cat?
You can Google this question and you’ll get all kinds of fun answers, like extra toes make polydactyls better climbers or hunters. Or that bigger paws make for better snowshoes in the snow. But there is absolutely zero scientific evidence that having extra toes make polydactyls “better” in any particular way – except for the extra toe-bean thing.
A devastating condition that can be mistaken for polydactyly
A cat with a disease called feline radial hypoplasia could form extra toes, but this is not polydactyly.
The mutation for this genetic disease is in a gene completely unrelated to polydactyly. This disease produces unusually small, twisted, or missing radius bones, one of the two important bones in a cat’s forearm.
Cats with this disease tend to sit up like a rabbit or kangaroo because having short front legs puts a strain on their spines and because it can be painful to put weight on deformed forelegs. Cats with radial hypoplasia can develop extra toes but their toes tend to look like additional fingers, rather than the mitten paw that many polydactyl cats have.
Are there cat breeders who breed polydactyl cats?
Some people love the look of extra toes so much that they want to go out and purchase a cat with this trait. But here’s something worth contemplating:
At one point, 40% of Maine Coon cats had extra toes, until breeders deliberately bred out the extra-toe trait. Today’s breed standard requires a “normal” paw: large and rounded with heavily tufted toes.
There is currently an attempt in the Netherlands and Belgium to bring back many-toed Maine Coons. But this effort is controversial. The fear is a “cat-toes arms race,” of sorts. Once extra toes become something to breed for, breeders may get carried away, trying to breed in as many toes as possible. How many toes is too many, before a cat becomes disabled by his toes?
Deliberately breeding for certain genetic mutations can be treading on dangerous ground. Read about the Manx cat and the Scottish Fold to learn more about what can happen to cats when humans want them to look a certain way.
There is at least one breed in which extra toes is considered acceptable: the Pixie-bob cat. The breed standard for this cat, who looks like a little lynx, allows Pixie-bobs to sport up to seven toes per paw.
What is the maximum number of toes that a cat can have?
The current Guinness Book of World Records record holder for the most toes is Jake, who had 28 total toes, as counted by a veterinarian.
The most famous polydactyl cat guardian
Nobel-prize winning author Ernest Hemingway was a cat lover in the extreme. He often wrote of his pets, once dedicating 35 pages to his beloved cat, Boise, in “Islands in the Stream.”
His former home (now a museum) in Key West, Florida is currently home to about 50 cats, about half of which have extra toes. It’s not clear where the multi-toed cats came from: legend has it that a ship captain and friend gifted Hemingway a white tom with extra toes called Snow White or Snowball and that all the Hemingway cats descended from this patriarch. It’s equally likely that the Hemingways had no pets at this house at all, and that the current feline residents were local ferals who moved in after the writer left.
Whatever the real story, cats with extra toes today are often referred to as “Hemingway cats” no matter where they live, and one of the mutations that causes extra toes in cats (the one that gives cats “mittens”) is often referred to as the Hemingway mutation.
The most famous polydactyl cat
U.S. President Theodore Roosevelt enjoyed the company of a polydactyl blue tabby he called Slippers. Slippers was given the run of the White House and often made himself a tripping hazard in hallways. Once, he flopped himself down in a corridor, forcing dignitaries to step awkwardly around his body in repose, on their way to a state dinner in the dining room.
As it should be, Slippers. As it should be.
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Dawn LaFontaine is a lifelong animal lover who always seems to have a little pet hair in her keyboard. Her blog, Kitty Contemplations, helps cat guardians better understand and care for the special beings they share their lives and homes with. Her cat-products business, Cat in the Box, sells beautiful, well-made, and award-winning products that she designed to meet the biological needs of cats.
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