A
digitigrade is an animal that stands or walks on its digits, or toes. Digitigrades include walking birds (what many assume to be bird knees are actually ankles), cats, dogs, and most other
mammals, but not
humans,
bears, and a few others (cf.
plantigrade,
unguligrade). They are generally quicker and move more quietly than other mammals.
While humans usually walk with the
soles of their feet on the ground, i.e.
plantigrade locomotion, digitigrade animals walk on their
distal and
intermediate phalanges. Digitigrade locomotion is responsible for the distinctive hooked shape of dog legs.
There are anatomical differences between a plantigrade and digitigrade
limb. Digitigrade animals have relatively long
carpals and
tarsals, and the bones which would correspond to the human
ankle are thus set much higher in the limb than in a human. This effectively lengthens the foot, so much so that a digitigrade animal's "hands" and "feet" are often thought to correspond only to what would be the bones of the human finger or toe.
Examples of digitigrades
Skeleton of a wolf, showing a typical digitigrade arrangement of leg and foot bones
