Tripedalism (from theLatintri = three +ped = foot) is locomotion by the use of three limbs. Real-world tripedalism is rare, in contrast to the commonbipedalism of two-legged animals andquadrupedalism of four-legged animals. Bilateral symmetry seems to have become entrenched very early in evolution, appearing even before appendages like legs, fins or flippers had evolved.[2]
It has been said thatparrots (birds of theorder Psittaciformes) display tripedalism during climbing gaits,[3] which was tested and proven in a 2022 paper on the subject, making parrots the only creatures to truly use tripedal forms of locomotion.[1] Tripedal gaits were also observed by K. Hunt[4] in primates. 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 somemacropods such askangaroos, 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 tripedallocomotion in animals. There are also thetripod fish. Several species of these fish rest on the ocean bottom on two rays from their twopelvic fins and one ray from theircaudal fin.[5]
There are some three-legged creatures in the world today, namely four-legged animals (such aspetdogs andcats) which have had onelimbamputated. With proper medical treatment most of these injured animals can go on to live fairly normal lives, despite being artificially tripedal. There are also cases ofmutations orbirth abnormalities in animals (including humans) which have resulted in three legs.[citation needed]