Claw

A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds).

Claws are used to catch and hold prey in carnivorous mammals such as cats and dogs, but may also be used for such purposes as digging, climbing trees, self-defense and grooming, in those and other species.

Claw-like projections that do not form at the end of digits but spring from other parts of the foot are properly named spurs.

Tetrapods use their claws in many ways, commonly to grasp or kill prey, to dig and to climb and hang.

Outside of the cat family, retractable claws are found only in certain species of the Viverridae (and the extinct Nimravidae).

Domesticated equids (horses, donkeys and mules) usually need regular trimming by a farrier, as a consequence of reduced activity on hard ground.

With the evolution of grasping hands and feet, claws are no longer necessary for locomotion, and instead most digits exhibit nails.

However, claw-like nails are found in small-bodied callitrichids on all digits except the hallux or big toe.

The hoatzin and turaco are unique among extant birds in having functional claws on the thumb and index finger (digits I and II) on the forelimbs as chicks, allowing them to climb trees until the adult plumage with flight feathers develop.

[9][10] However, several birds have a claw- or nail-like structure hidden under the feathers at the end of the hand digits, notably ostriches, emus, ducks, geese and kiwis.