Mitten cats, Hemingway cats, thumb cats. Whatever you call them, cats with extra toes are undeniably adorable. Technically known as polydactyl, these cats have more than the normal 18 digits. If you have one of these unusual cats, count yourself lucky.
Polydactyly in cats is a mutation that is passed along as a dominant trait. That means that if a kitten inherits one copy of the gene from either Papa or Mama Cat, he will have more than the standard 18 toes—five on each front paw and four on each hind paw. How many extra toes he has, though, varies, and is not necessarily the same number of extras his parent has. The current record holder is a ginger tabby named Jake, with 28 toes!
If the extra toes are on the thumb side or inside of the paw, this is technically called the pre-axial form of polydactyly. These cats are often called "mitten cats," because the cat’s paws look like mittens. If the extra toes are on the outer side of the paw, this is technically referred to as post-axial and is a less common form. Polydactyly is most often seen only in the front paws, although some cats have extra toes on all four paws. Interestingly, the condition isn’t seen in back paws only.
Extra-toed cats are most common along the East Coast of the United States and in southwest England. Boston, in particular, has a large population, strengthening the theory that sailors traveling to the New World brought extra-toed cats to the Colonies because they were adept at climbing and catching rodents on board their ships. Indeed, owners of polydactyls often report that their kitty is quite dexterous with his thumb!
The cats are often referred to as Hemingway cats because Ernest Hemingway had a well-known love for them, and even more than 50 years after his death, about 50 polydactyl cats reside on the grounds of the museum that was once the author’s home in Key West.
Extra toes in cats by themselves are harmless, and polydactyls are just as healthy as other cats. There is a rare, severe condition, however, called radial hypoplasia, in which the radial bones of the cat’s forearm are not developed. Cats with this serious condition cannot walk normally, and one corresponding feature of the abnormal radial bones is the presence of extra toes. Your vet will be able to easily determine if your cat has this condition.
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