Adrienne is a certified professional dog trainer, dog behavior consultant and former veterinarian assistant for an AAHA animal hospital.
What Is Polydactyly in Dogs?
Polydactyly is simply a term that has been used over the years to depict animals who are blessed with extra toes.
You may have heard the first time about polydactyly from the writings of Ernest Hemingway. This author loved cats, and his son was once gifted a kitten that was blessed with six toes.
This kitten bred with the local cats, creating a whole line of cats carrying the polydactyl gene.
Among dogs, the number of toes on a dog's paws varies from breed to breed. Certain breeds have more toes than others. Let's discover some of them!
How Many Toes Does the Average Dog Have?
If we look at the number of toes of various animals, we may notice that there is a general trend to have four or five toes at the end of a limb.
For example, humans have five fingers and toes and so do bears, primates, weasels, bats, and several types of reptiles.
However, several animals such as dogs, foxes, wolves and coyotes though have only four fully functional toes rather than five. What's up with these animals? Why are they missing the extra toes?
Fossil evidence shows that animals that show a loss of digits are for the most part animals who were built to maintain high speeds for long distances, explains John Buckwalter, Emeritus of Biology at Alfred State College.
Such animals are known as "cursorial animals." The specific features of these animals consist of long legs, shortened digits and a reduced number of toes.
The reduced number of toes helps improve velocity, considering that an extra digit could ultimately make quite a difference.
Although at a first glance, it may just weigh a few ounces, consider its impact when it's piggy-backed along for the ride when the animal runs whether to catch his dinner or away from somebody who wants to eat him for dinner!
On top of reducing the number of toes, evolution also caused a dog's legs to move forward in a way that their heels no longer made contact with the ground as it happens with us human plantigrades.
By walking on their toes, dogs, therefore, became “digitigrades." This feature, along with the longer forelegs, allowed extra speed, causing dogs to be classified, as mentioned earlier, as "cursorial," that is, animals specifically built for running.
Read More From Pethelpful
Presence of Dewclaws
If you have heard about most dogs having five toes on each front foot and four toes on each hind foot, it's because an extra toe has been added to the count.
This fifth toe located upper in the front feet is known as the 'dewclaw' and is the equivalent of our thumb.
A dog's dewclaw is not fully functional though as the other toes are and therefore doesn't make constant contact with the ground as the other toes do. It is not attached to the paw, but is rather attached to the wrist part of the dog's paw.
However, research has revealed that dewclaws do
Despite its several uses, the dewclaw though is often removed so to prevent it from getting caught into things or for a cleaner look in the show ring. This is done when the puppy is very young, usually at 2 to 5 days of age.
An Ancestral Trait
Did you know? Your dog's dewclaws are believed to be a remnant from his distant past—as in over 40 million years ago—when Rover's ancestors (a tree-climbing cat-like animal known as Miacis) used to climb trees.
Later on though, as a dog's ancestors evolved into a ground-dwelling species (Cynodictis) they started to rely more on speed and agility to capture prey, therefore the use of this extra toe became redundant.
This has caused it to recede into the vestigial anatomical feature we see today, points out Stanley Coren in the book Do Dogs Dream? Nearly Everything Your Dog Wants You to Know.
On top of having dewclaws on their front legs, in some cases, there may also be dogs boasting extra toes in their back legs, which are discussed next.
What Dog Breeds Have Extra Toes in Their Back Legs?
Not many dog breeds have extra toes in their back legs. A study has revealed that the appearance of this fifth toe is an evolutionary throwback to a dog's ancestral past. This further seems to prove Coren's earlier observations.
Several of these breeds were historically used to guard flocks as livestock guardians or evolved for harsh conditions. Following are several dog breeds with extra toes in their back legs.
The great Pyrenees is blessed with ﬁve or six digits that have been intentionally maintained through selective breeding. They have front legs with single dewclaws and back legs with double dewclaws.
According to the American Kennel Club's standard, the front legs should carry single dewclaws, which should not be removed. While the back legs may have double dewclaws, single dewclaws or even no dewclaws, although their presence is preferable, being an ancient breed characteristic.
These dogs may have dewclaws on their front legs and double dewclaws on their hind legs. The dewclaws may be removed though.
These extra toes helped the herd livestock and navigate rugged landscapes, allowing better stability and friction.
These dogs have front dewclaws which may be removed and rear dewclaws (even double) which may be also removed.
These dogs have front dewclaws which may or may not be removed. In the back legs, two dewclaws are required, each placed low by the rear leg, placed low on the leg, ideally forming additional functioning toes. Having less than two dewclaws on each rear leg is means for disqualification in the show ring.
In this breed, the double dewclaws present close to the foot and form well-separated "thumbs" with nails. Anything less than double dewclaws is means for disqualification in the show ring.
Norwegian Lundehund: The Dog Breed With Six Toes
The Norwegian Lundehund is blessed with a distinct foot structure. This dog breed's feet sport six fully developed toes on each foot along with elongated rear foot pads.
On the front feet while standing, expect to see five of the six toes making contact with the ground, while on the back foot; at least four of the six toes are expected to rest on the ground.
Rarely do we see such polydactyl mutations involving both the front and back legs!
These fascinating features helped this unique dog cling to steep vertical cliffs as he hunted for puffins in their rugged ad almost inaccessible nesting locations.
Not What it Looks Like
Sometimes, dog owners report that their dog has an "extra toe" or an "extra nail," when in reality, they are looking at what's known as a "cutaneous horn".
A cutaneous horn is often caused by the papillomavirus, and it should be removed and sent out for biopsy.
- Park, K., Kang, J., Subedi, K. P., Ha, J. H., & Park, C. (2008). Canine polydactyl mutations with heterogeneous origin in the conserved intronic sequence of LMBR1. Genetics, 179(4), 2163–2172.
- MadSci Network, Why do dogs have dewclaws? and why are they only in the front? ohn Buckwalter, Professor, Physical and Life Sciences, SUNY College of Technology, Alfred, NY
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.
© 2022 Adrienne Farricelli