Why Do Some Maine Coons Have Six Toes? Polydactyl Maine Coon Genetics Explained

Maine Coons are famous for their impressive size and large paws. But sometimes, when looking closely at a kitten's paws, an owner may discover six, seven or even more toes instead of the usual number. This anatomical feature is called polydactyly.

Polydactyl Maine Coons attract considerable interest among cat owners and breeders. They are sometimes called six-toed cats or “mitten cats”. However, behind their unusual appearance lies a fascinating hereditary mechanism studied by modern feline genetics.

How many toes does a cat normally have?

Most domestic cats have 18 toes: five on each front paw and four on each hind paw.

With polydactyly, one or more additional digits develop. Their number and position can vary considerably, even among related cats.

Extra toes may occur only on the front paws or may affect several limbs. This is why the paws of polydactyl cats can look very different from one animal to another.

What is polydactyly?

Polydactyly is a congenital anatomical trait in which an animal develops more digits than usual.

In Maine Coons, non-syndromic forms of polydactyly are known. In such cases, the additional digits are a feature of limb development and do not, by themselves, mean that the cat has a disease.

Why do some Maine Coons have extra toes?

The Maine Coon developed as a natural cat population in North America. Polydactyl cats historically occurred in this region, and the trait has remained present in certain Maine Coon breeding lines.

Modern genetic research confirms that polydactyly in Maine Coons has a hereditary basis.

How is polydactyly inherited in Maine Coons?

Research indicates that polydactyly in Maine Coons can be inherited as an autosomal dominant trait.

This means that a cat may develop the trait after inheriting the relevant genetic variant from only one parent.

However, inheritance cannot always be reduced to the simple formula “the gene is present, therefore extra toes must appear”.

Researchers have described incomplete penetrance and variable expressivity. In simple terms, the same inherited trait may appear differently in different cats.

One Maine Coon may have only one additional digit, while another may have several. Their position and anatomical development may also vary.

Which genetic mechanisms are associated with polydactyly?

Genetic studies of feline polydactyly have identified variants in a regulatory region known as ZRS.

This regulatory region is involved in controlling the activity of the SHH signalling pathway, which plays an important role in limb development during embryonic growth.

ZRS is located within the LMBR1 gene, but its importance in polydactyly is primarily connected with the regulation of SHH activity during limb formation.

Changes affecting this developmental mechanism can influence the number and arrangement of digits.

Why is the genetics of polydactyl Maine Coons especially interesting?

Scientific studies have demonstrated that polydactyly in Maine Coons may have different genetic causes.

In some polydactyl cats, researchers identified the known Hw genetic variant, which had previously been described in polydactyl cats.

However, other polydactyl Maine Coons did not carry the known variants investigated in the study.

This led researchers to describe genetic heterogeneity of polydactyly in Maine Coons. In other words, a similar visible trait does not necessarily have exactly the same genetic cause in every breeding line.

Will a polydactyl Maine Coon always produce polydactyl kittens?

No. Even when a trait has a dominant mode of inheritance, it does not mean that every kitten produced by a polydactyl parent will necessarily have additional toes.

The outcome depends on the parents' genotypes, the characteristics of the particular breeding line and the expression of the inherited trait.

For this reason, breeders should evaluate results across several generations rather than drawing conclusions from a single mating.

Are extra toes dangerous for a cat?

Non-syndromic polydactyly does not automatically mean that a cat is unhealthy.

Nevertheless, unusual paw anatomy requires attentive routine care. Owners should regularly examine every digit and claw.

Some additional claws may be positioned in a way that prevents them from wearing down naturally. If a claw becomes ingrown, repeatedly injured, causes discomfort or interferes with normal movement, the cat should be examined by a veterinarian.

Should extra toes be surgically removed?

The presence of an additional digit alone is not an automatic indication for surgery.

Any decision concerning medical or surgical intervention should be made by a veterinarian after examining the individual animal.

If the paw functions normally and the additional digit does not cause pain or recurrent injury, the need for surgical treatment should be considered individually.

What should breeders consider?

Breeding polydactyl Maine Coons should not focus exclusively on the spectacular appearance of their paws.

Breeders should record the number of digits in every kitten, the position of additional digits, the structure of the parents' and offspring's paws, and the results of previous matings.

Clear photographs of each kitten's paws can also be valuable. Such records help breeders monitor how the inherited trait is expressed within a particular breeding line.

Polydactyly and pedigrees

Reliable information about ancestry is especially important when working with inherited traits.

A pedigree allows breeders to analyse several generations, identify recurring characteristics and make better-informed decisions when selecting breeding pairs.

Registered pedigree information can also be verified through the official WCA Pedigree Check service.

WCA standard for the Polydactyl Maine Coon

The World Cat Association has published a dedicated breed standard for the Maine Coon Polydactyl (MCP).

Breeders working with polydactyl Maine Coons should follow the current WCA standard rather than relying only on photographs found on social media or general assumptions about “six-toed Maine Coons”.

Polydactyly should not be the only breeding objective

Extra toes can make a Maine Coon particularly distinctive, but a responsible breeding programme cannot be based on a single physical characteristic.

When selecting a breeding pair, breeders should consider health, breed type, temperament, ancestry, genetic diversity and health examinations recommended for the breed.

Polydactyly should therefore be regarded as one characteristic of the animal rather than a substitute for a complete breeding evaluation.

What should you check when buying a polydactyl Maine Coon kitten?

Prospective owners should obtain information about the kitten's ancestry and parents and carefully examine the kitten's paws.

It is important to evaluate not only the number of additional digits but also their functionality, the condition of the claws and whether the kitten shows any signs of discomfort.

Buyers may also ask the breeder whether polydactyly has appeared in previous generations and whether related cats have experienced any problems associated with additional digits or claws.

Key facts about Polydactyl Maine Coons

Polydactyly is an inherited developmental trait in which a cat develops additional digits.

In Maine Coons, this trait has a fascinating and genetically heterogeneous background. Modern research has linked some cases to variants affecting the ZRS regulatory region, while currently known variants do not explain every polydactyl Maine Coon line.

For professional and responsible breeding, accurate records, reliable pedigrees, observation across several generations and careful attention to animal health are therefore particularly important.

Scientific source

Hamelin A. et al. Genetic heterogeneity of polydactyly in Maine Coon cats. Journal of Feline Medicine and Surgery, 2020.

World Cat Association (WCA)
International Feline System