An extra-toes cat is not a breed but any cat born with polydactyly, a harmless genetic variation that adds digits to one or more paws. A typical cat has 18 toes, while polydactyls often have six or seven on a front paw, sometimes creating a mitten-like thumb. The trait is dominant, so one affected parent can pass it to roughly half of a litter. It is especially common in New England and Atlantic Canada, where ship cats with big paws were prized as mousers.
The nickname comes from Ernest Hemingway, who was given a six-toed cat named Snow White; dozens of descendants still live at his Key West home. Most extra-toed cats in shelters are domestic shorthairs or longhairs, and their personalities are as varied as any cat's. The main care difference is nail trimming, since extra claws can curl into the paw pads.