The dew claw gets its name from its position on the leg. Sitting higher up than the other toes, this small digit never touches the ground during normal walking. It only brushes the dew on the tops of grass blades, skimming the surface without making solid contact with the earth below. That image of a claw that merely grazes the morning dew is what gave it the name.
What a Dew Claw Actually Is
A dew claw is a reduced digit found on the inner side of the leg in dogs, cats, and several other animals. On a dog’s front leg, it sits roughly where your thumb would be, and that comparison is more than casual. The dew claw is the biological equivalent of the first digit, the same one that became the human thumb over millions of years of evolution. In most dogs, the front dew claws are attached to bone and have a small but real skeletal structure connecting them to the rest of the foot.
Rear dew claws are a different story. When they appear on the hind legs, the first and second toe bones are often missing entirely. The claw and whatever small bone remains are attached only by skin and fibrous tissue, making them floppy and loosely connected. This is why rear dew claws are sometimes described as “dangling” from the leg.
Why Dogs Still Have Them
Dew claws are vestigial structures, features inherited from ancestors that once had more functional toes. Early carnivores walked on five fully developed digits per foot. As canines evolved for endurance running over open ground, they shifted their weight to fewer toes, and the innermost digit gradually moved up the leg and shrank. It no longer needed to bear weight, so evolutionary pressure to maintain it largely disappeared.
That said, front dew claws are far from useless. When dogs run at high speeds, their front feet bend enough that the dew claw makes contact with the ground. During sharp turns or movement on slippery surfaces, the dew claw provides extra traction and helps stabilize the wrist joint. Dogs also use their dew claws to grip bones, toys, or sticks while chewing, and some breeds use them for climbing. The front dew claw functions a bit like a biological kickstand: not always engaged, but important when it is.
Rear Dew Claws and Breed Genetics
Most dogs have front dew claws, but rear dew claws are less common and appear only in certain breeds. Genetic research has linked rear dew claws to a region on canine chromosome 16, with the trait following a dominant inheritance pattern. If a dog carries one copy of the relevant gene variant, it will typically develop hind dew claws.
Some breeds are expected to have rear dew claws as part of their breed standard. The Great Pyrenees, Beauceron, Briard, and Icelandic Sheepdog all commonly have double dew claws on each hind leg. In the Great Pyrenees, these extra digits have a bone structure similar to front dew claws and may offer some functional benefit on the rough, mountainous terrain these dogs were bred to work on. When two dew claws appear on the same leg, there can be a complete duplication of the toe bones and the connecting foot bone.
Dew Claws in Other Animals
Dogs aren’t the only animals with dew claws. Pigs, cattle, and deer all have them, though the anatomy differs based on which digits were reduced. In cattle, each leg has two main weight-bearing toes (the third and fourth digits) and two smaller dew claws (the second and fifth digits). These dew claws sit behind and above the main hooves and normally don’t contact the ground. On soft, deep, or steep terrain, however, they splay outward and provide extra support, preventing the animal from sinking or slipping.
The pattern across species is consistent: ancestors had five toes, and as different lineages adapted to different environments, some digits shrank or disappeared. Pigs lost the first digit completely, reduced the second and fifth to dew claws, and kept only the third and fourth as functional hooves. Dogs kept the first digit as their dew claw while shifting weight primarily to the third and fourth toes, with the second and fifth providing side-to-side balance.
Why Dew Claws Need Extra Care
Because dew claws don’t touch the ground during regular walking, they never wear down the way a dog’s other nails do. Without trimming, they can curl back into the skin, becoming ingrown and potentially infected. Most dogs need their dew claws trimmed every four to six weeks.
Overgrown dew claws are also more likely to snag on fabric, brush, or carpet and tear. A torn dew claw can bleed heavily and is painful. In some cases, the entire claw gets ripped away from the leg. Signs of a dew claw infection include redness, swelling, warmth around the nail, discharge or pus, a foul smell, and persistent licking at the spot. Even minor tears are worth having examined, since bacteria can enter through the broken nail and cause an infection that spreads deeper into the paw.
Regular inspection is especially important for rear dew claws, which tend to be loosely attached and more vulnerable to catching on things. Keeping them trimmed short significantly reduces the risk of a painful snag or tear.