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Why Do Some Dogs Have Extra Claws on Their Hind Feet?

Sophie Jackson is a dog lover and trainer living in the UK. She competes in agility and obedience with her four dogs.

Nearly all dogs are born with front dewclaws, however rear dewclaws are rarer

Nearly all dogs are born with front dewclaws, however rear dewclaws are rarer

When you look at your dog's hind feet, do you see an extra claw on the inside of their leg? It might appear to be a full toe, or it might be a loose piece of skin with a claw at the end.

A typical canine paw consists of four toes that sit together to create the main part of the foot with an additional fifth toe sitting further up the leg. This toe is called a dewclaw. It is sometimes compared to a human thumb and it acts as a stabiliser for the wrist. In some countries it is common practice to remove these dewclaws shortly after a puppy is born, however, this can lead to complications.

Occasionally, puppies are born with a declaw on their hind feet as well. This is far less common and often these extra toes are poorly formed, lacking bone and sticking out from the foot. These claws can lead to problems and many vets like to remove them, but before you make a decision on your dog's rear fifth toe, it is important you know the facts behind the claw.

The Evolution of Dewclaws

The canine dewclaw (both front and hind) is a curious feature because the dog's ancestor, the wolf, does not have dewclaws at all. It appears the dewclaw developed after the evolution of the domestic dog. Research on wolves that have dewclaws found that their DNA indicated they were the product of dogs and wolves interbreeding and not an indication that wolves once had dewclaws.

The canine front dewclaw is therefore slightly curious. It is a highly versatile digit that can be used for digging, climbing, grasping and for strengthening the wrist when making sharp turns. It must have granted an advantage to the earliest dogs who possessed them, making them more likely to survive and breed, thus passing on the gene for dewclaws to their offspring. So important was the dewclaw as an evolutionary step, that now nearly all dogs are born with front dewclaws.

Hind dewclaws are harder to explain as they don't appear to offer obvious benefits to the performance or survival of the animal. In fact, scientists argue they should not be called dewclaws at all, but Polydactyl Mutations (extra toes). According to a scientific paper published in the science journal Genetics in 2008, polydactyl mutations are caused by a single gene (LMBR1) which restores this fifth toe which has otherwise been lost through canine evolution.

No one is sure what purpose this toe might have once served, though it has been suggested it may have helped early dogs to climb, and in some breeds that are specifically bred to have rear dewclaws, they are still considered to serve this purpose. However, clearly there was no great advantage for the majority of dogs in having rear dewclaws, in comparison to front dewclaws, and so they were gradually lost as the domestic dog evolved.

Pure wolves do not have hind dewclaws, though some wolf-dog hybrids do

Pure wolves do not have hind dewclaws, though some wolf-dog hybrids do

What Do Rear Dewclaws Look Like?

Unlike front dewclaws which are fully formed fifth toes with bone, rear dewclaws come in various forms and often lack bone.

The commonest type of rear dewclaw is just a fleshy protuberance with a claw at the end. Even in breeds bred to have 1 or 2 rear dewclaws, they often appear this way. The toe may stick out at an odd angle from the leg.

In other dogs, the rear dewclaws are fully articulated toes. They have jointed bones inside and sit tightly against the leg. In this case, the toe is fully developed and must be close to the type of rear dewclaw the earliest dogs had.

Border collie/Bernese cross puppy with double rear dewclaws

Border collie/Bernese cross puppy with double rear dewclaws

Should Rear Dewclaws Be Removed?

Unlike front dewclaws which are important for stabilising the wrist joint, rear dewclaws do not appear to have a functional purpose. People sometimes think it is best to have them removed to prevent injury, however, injuries to rear dewclaws are not as common as people fear and in some breeds rear dewclaws are a requirement of the breed standard and should not be removed.

Rear dewclaws that stick out from the foot and are not articulated by bone can be at risk of catching and being injured. If these are not removed when the dog is a puppy (always by a veterinarian) then it may be an option to have them removed when another surgical procedure is being carried out, such as when the dog is spayed or neutered. Consideration should be made to the necessity of this removal, as this will require a general anaesthetic which can carry risks of its own.

Rear dewclaws that are an actual bony toe and sit flush to the foot are a more complicated matter, since they are effectively a true toe with nerves running through them. It is not fully understood if removing such a toe could lead to similar issues that occur from removing front dewclaws, including the withering of the nerves that were in the toe.

Usually, these types of rear dewclaw are so solid and neat to the foot they cause no problem for the dog's well being and once again consideration must be taken as to whether putting a dog through an operation to remove claws that cause no issue is really necessary.

Many vets now prefer to leave dewclaws (rear and front) alone and only advise removing them if they are severely injured.

When debating your dog's rear dewclaws and whether they should be removed, consider that some breeds are expected to have single or double rear dewclaws and they do not suffer problems because of them.

Pyrenean Mountain Dogs are one breed that should have double rear dewclaws

Pyrenean Mountain Dogs are one breed that should have double rear dewclaws

Which Breeds Should Have Rear Dewclaws?

While any dog can be born with rear dewclaws, in most breeds this is unusual and considered a genetic throwback. Only in a handful of breeds is that extra fifth toe perceived as a valued trait; a feature the dog should have to conform with the breed standard. Some breeds are even expected to have double-dewclaws on their rear feet, effectively six toes. In these breeds, the removal of the dewclaws is undesirable.

The following breeds should have rear dewclaws.

  • Pyrenean Mountain Dog (Great Pyrenees): single or double-dewclaws
  • Icelandic sheepdog: double preferred
  • Cao Fila de Sao Miguel: single rear dewclaws
  • St Bernard: only accepted as breed standard in some countries
  • Estrela Mountain dog: single or double
  • East Siberian Laika: double
  • Anatolian Shepherd: double
  • Beauceron: double and well-spaced
  • Catalan sheepdog: double
  • Briard: double

The Norwegian Lundehund dog is extra special as it is not only expected to have double-dewclaws on its rear paws but also six toes on its front paws too. These additional toes are believed to be responsible for the dog's extreme agility which it needs for its traditional role of puffin hunting.

The Lundehund was expected to clamber up sheer cliffs after the birds and those extra toes are thought to have given them the gripping power they needed.

In some countries the St Bernard breed standard states they can have rear dewclaws

In some countries the St Bernard breed standard states they can have rear dewclaws

How to Take Care of Rear Dewclaws

Basic maintenance of rear dewclaws will prevent them from ever becoming a problem. They require similar maintenance to the rest of your dog's claws. Claw clipping or filing should be part of your grooming regime for your dog, no matter the breed. Claws easily become too long, even when a dog regularly walks on concrete and this can lead to the claws snagging or being injured.

Rear dewclaws rarely touch the ground, so for many dogs, this claw is never naturally worn down. To prevent the claw curling around and growing into the toe or leg, it should be trimmed regularly. A weekly pedicure will help keep all your dog's claws neat and short. This also enables you to look for any injuries or problems with the foot.

Aside from trimming rear dewclaws, there is no special care that needs to be taken with them, unless a dog has caught or torn them in the past. Keeping the dewclaw short will usually avoid these problems.

Dogs with rear dewclaws are not detrimentally affected by them, they do not impede movement, unless allowed to become overgrown (which is the same for any claw on your dog's feet) and many dogs go through their whole lives having no issues with them.

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.