Tripedalism

Bilateral symmetry seems to have become entrenched very early in evolution, appearing even before appendages like legs, fins or flippers had evolved.

This is usually observed when the animal is using one limb to grasp a carried object and is thus a non-standard gait.

Apart from climbing in parrots, there are no known animal behaviours where the same three extremities are routinely used to contact environmental supports, although the movement of some macropods such as kangaroos, which can alternate between resting their weight on their muscular tails and their two hind legs and hop on all three, may be an example of tripedal locomotion in animals.

[5] There are some three-legged creatures in the world today, namely four-legged animals (such as pet dogs and cats) which have had one limb amputated.

There are also cases of mutations or birth abnormalities in animals (including humans) which have resulted in three legs.

Male cockatiel climbing from a log to a ladder using his beak. In 2022, it was proven that parrots use their necks and heads as a third limb with propulsive and tangential forces equal to or greater than those forces generated by forelimbs in non-human primates when climbing vertical surfaces. [ 1 ]
Four-legged animals such as dogs sometimes lose limbs and become artificially tripedal.