Polydactyly is a common genetic anomaly in domestic cats defined by the presence of extra digits on one or more of their paws. A typical cat possesses 18 toes in total, with five digits on each front paw and four on each back paw. This inherited trait results in a higher-than-average toe count, often giving the cat an unusually large or wide paw appearance. It is a simple, non-pathological trait.
The Defining Features of Polydactyly
The physical manifestation of feline polydactyly varies considerably in the number and arrangement of the additional digits. While the standard count is 18, polydactyl cats frequently have as many as 22 to 28 toes. The extra toes are most commonly found on the front paws, though they can appear on all four limbs.
The condition is often classified based on the morphology of the paw. The “patty paw” configuration, or post-axial polydactyly, features extra digits arranged in a simple row, making the paw appear wider. The pre-axial form is known colloquially as the “mitten paw.” In this configuration, the extra toe is positioned adjacent to the dewclaw, giving the illusion of a thumb.
The Genetic Mutation Responsible
The underlying cause of polydactyly is a spontaneous mutation within a single regulatory gene that governs limb development. This trait is conferred by an autosomal dominant gene, often called the Pd gene. Only one copy of the mutated allele is needed for the cat to exhibit the condition. Because the gene is dominant, the inheritance pattern ensures a high probability of passing the trait to offspring.
The specific genetic mechanism involves a point mutation within the ZRS (ZPA Regulatory Sequence) enhancer region. This region controls the expression of the Sonic hedgehog (Shh) gene, a powerful morphogen responsible for patterning the anterior-posterior axis of a developing limb. The mutation causes the Shh gene to be expressed in an abnormal location or for a longer duration during embryonic development, leading to the formation of supernumerary digits.
This genetic modification is considered benign and is distinct from other forms of limb malformation. The polydactyly mutation is not linked to serious health complications or neurological issues. The extra digits are usually fully formed with their own bone structure, claws, and nerve supply, allowing for normal function and movement.
Does Polydactyly Affect Movement or Behavior
For most polydactyl cats, the presence of additional toes has no negative impact on their mobility or quality of life. The skeletal structure of the paw is simply modified to accommodate the extra digits, and the cat learns to move and balance as any standard-toed feline would. The broader surface area created by the polydactyl paw can sometimes offer a slight advantage in certain environments.
The larger paws provide greater stability and weight distribution. This may make these cats more adept at traversing uneven terrain, such as snow or loose dirt. The pre-axial “mitten paw” configuration, with its mobile, thumb-like digit, can occasionally be used to manipulate objects or gain a better grip while climbing. This enhanced physical capability is purely structural and does not translate to any difference in temperament or intelligence.
Historical accounts sometimes suggested that polydactyl cats were better hunters or luckier. These beliefs are unfounded, as the condition is purely morphological. Behavioral patterns are determined by breed, socialization, and individual personality, and the cats maintain typical, active feline behaviors.
Famous Polydactyl Cats and Historical Context
The prevalence of polydactyl cats has a long connection to maritime history and the transatlantic trade routes. Sailors frequently kept these wide-pawed cats aboard ships, believing the extra digits made them superior mousers with better balance on rolling decks. The cats were also widely regarded as symbols of good luck, which contributed to their spread from ports in New England, Nova Scotia, and the United Kingdom.
This historical distribution pattern explains why the trait is still concentrated in these geographical areas today. The most famous lineage traces back to the American author Ernest Hemingway. Hemingway was gifted a white polydactyl cat named Snow White by a ship captain in Key West, Florida, during the 1930s.
The descendants of Snow White continue to reside at the Hemingway Home and Museum, now numbering over 50 cats, nearly half of which exhibit the polydactyl trait. Polydactyl cats are often affectionately referred to as “Hemingway Cats.”