A dew claw is a fifth toe that does not make contact with the ground when the dog stands or walks. It is usually found on the front limbs, though some dogs also have dew claws on their hind legs.
Dew claws are similar, in terms of their position on the limb, to the human thumb. However, unlike thumbs, they cannot touch any of the other toes on a dog's paw, and they are considered largely nonfunctional. Many breed standards call for them to be removed, either because of aesthetics or to prevent injury.
Dew claws can become ingrown and may snag on brambles or carpet, so the traditional thinking favored removing them. As of 2015, most experts favor leaving dew claws in place. Dew claws, although a disadvantage in some activities, such as hunting through brush, may provide the dog an advantage in agility training or sheep herding.