Dewclaw

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For the web-comic characters of the same last name, see Kevin and Kell.
Paw of a dog: A. Claw, B. Digital pads, C. Metacarpal pad, D. Dewclaw, E. Carpal pad
A dog's dewclaw does not make contact with the ground while the dog is standing. This older dog's dewclaw is rounded from use while running, but it has grown.
Some active dogs' dewclaws make more frequent contact with the ground while running, so they wear down naturally, as do their other claws.
Double dewclaws on rear leg of dog

A dewclaw is a

unguligrade species, it does not make contact with the ground when the animal is standing. The name refers to the dewclaw's alleged tendency to brush dew away from grass.[1] On dogs and cats, the dewclaws are on the inside of the front legs, similarly to a human's thumb, which shares evolutionary homology.[2] Although many animals have dewclaws, other similar species do not, such as horses, giraffes and the African wild dog
.

Dogs

nail
on the dewclaw often wears down in the same way that the nails on their other toes do, from contact with the ground. In many dogs, the dewclaws never contact the ground. In this case, the dewclaw's nail never wears away, and it is often trimmed to maintain it at a safe length.

The dewclaws are not dead appendages. They can be used to lightly grip bones and other items that dogs hold with the paws. In some dogs, these claws may not appear to be connected to the leg at all except by a flap of skin; in such dogs, the claws do not have a use for gripping as the claw can easily fold or turn.[4]

Rear dewclaws

phalanx bones and are attached by skin only.[7]

Dewclaw removal

There is some debate as to whether dewclaws should be surgically removed.[1][8] The argument for removal states that dewclaws are a weak digit, barely attached to the leg, and thus they can rip partway off or easily catch on something and break, which can be painful and prone to infection. Dewclaw removal is most easily performed when the dog is young, around 2–5 days of age. It can also be performed on older dogs if necessary though the surgery may be more difficult then. The surgery is fairly straightforward and may be done with local anesthetics if the digit is not well connected to the leg. Many dogs cannot resist licking the surgery site in the weeks following the procedure, so an Elizabethan collar or bitterant may be used to curtail this behavior, thus preventing infection.[citation needed]

Some pups are commonly sold by breeders "dew-clawed", that is with the dewclaws removed (as by a veterinarian) for perceived health and safety reasons. A few breed standards, such as that for Portuguese Water Dogs, also call for it.

Dewclaws and locomotion

Based on stop-action photographs, veterinarian M. Christine Zink of Johns Hopkins University believes that the entire front foot, including the dewclaws, contacts the ground while running. During running, the dewclaw digs into the ground preventing twisting or torque on the rest of the leg. Several tendons connect the front dewclaw to muscles in the lower leg, further demonstrating the front dewclaws' functionality. There are indications that dogs without dewclaws have more foot injuries and are more prone to arthritis. Zink recommends "for working dogs it is best for the dewclaws not to be amputated. If the dewclaw does suffer a traumatic injury, the problem can be dealt with at that time, including amputation if needed."[2]

Cats

Members of the cat family – including domestic cats[9] and wild cats like the lion[10] – have dewclaws. Generally, a dewclaw grows on the inside of each front leg but not on either hind leg.[11]

The dewclaw on cats is not vestigial. Wild felids use the dewclaw in hunting, where it provides an additional claw with which to catch and hold prey.[10]

Hoofed animals

Capreolus capreolus
), with dewclaws

Hoofed animals walk on the tips of special toes, the

Cloven-hoofed animals walk on a central pair of hoofs, but many also have an outer pair of dewclaws on each foot. These are somewhat farther up the leg than the main hoofs, and similar in structure to them.[12] In some species (such as cattle) the dewclaws are much smaller than the hoofs and never touch the ground. In others (such as pigs and many deer), they are only a little smaller than the hoofs, and may reach the ground in soft conditions or when jumping. Some hoofed animals (such as giraffes and modern horses) have no dewclaws. Video evidence suggests some animals use dewclaws in grooming or scratching themselves or to have better grasp during mating.[citation needed
]

References

  1. ^ a b c d Danziger, D., & McCrum, M. (2008). The Thingummy: A book about those everyday objects you just can't name. London: Doubleday.
  2. ^ a b Zink, M. Christine. "Form Follows Function – A New Perspective on an Old Adage" (PDF). Penn Vet Working Dog Center. p. 11. Archived from the original (PDF) on 4 March 2016. Retrieved 8 November 2015.
  3. ISBN 978-0-7641-3887-4
    .
  4. ISBN 978-0-7216-7665-4
    .
  5. ISBN 0-87196-871-1
    .
  6. ^
    PMID 18689889
    .
  7. ISBN 978-0-7506-3599-8
    .
  8. ^ Lotz, Kristina N. "The Dewclaws Debate – Keep Them or Lose Them?". iheartdogs.com. Retrieved 8 November 2015.
  9. ^ "Clipping a Cat's Claws (Toenails)". Pet Health Topics. Washington State University College of Veterinary Medicine. 22 July 2009. Archived from the original on 4 November 2013. Retrieved 2 November 2013. Cats have a nail on the inner side of each foot called the dew claw. Remember to trim these as they are not worn down when the cat scratches and can grow in a circle, growing into the foot.
  10. ^ a b "Physiology". Lion ALERT. Retrieved 2 November 2013. Lions have four claws on their back feet but five on the front where the dew claw is found. This acts like a thumb and is used to hold down prey while the jaws rip away the meat from bone. Set well back from the other claws the dew claw does not appear in the print.
  11. ^ Bircher, Steve (5 November 2011), Tiger Tales (PDF), National Tiger Sanctuary, archived from the original (PDF) on 3 November 2013
  12. ISBN 978-1-58923-129-0
    .
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