Tripedalism

Tripedalism (from the Latin tri = three + ped = foot) is locomotion by the use of three limbs. Real-world tripedalism is rare, in contrast to the common bipedalism of two-legged animals and quadrupedalism 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]

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]

In nature

Parrots (birds of the order Psittaciformes) are the only creatures to naturally use tripedal forms of locomotion, as they use their heads as a third limb when climbing.^[1] Non-standard tripedal gaits are also observed in primates when they use one limb to grasp an object.^[3]

Quadrupedal amputees and mutations

 

Four-legged animals such as dogs have been documented as capable of adapting to live with three legs, being made artificially tripedal through amputation surgery

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. Animals made into tripeds through amputation may suffer from long term health consequences; these issues include osteoarthritis and spinal deformity and are largely a result of disruption to natural locomotion cycles and symmetry.^[4]

 

Health consequences vary depending on which limb was lost, with hind legs being less consequential of a loss than front legs in quadrupeds like dogs

There are also cases of mutations or birth abnormalities in animals (including humans) which have resulted in three legs. With humans, a third limb may arise from the surgical bisection of conjoined or parasitic twins. Such conditions will often result in a limb with reduced or limited mobility. In rarer cases such as with Frank Lentini, a third limb may be usable in activities requiring moderate motor function, such as kicking a football, but will still lack the fine motor skills of the natural limbs.^[5]

See also

• Bipedalism
• Quadrupedalism
• Terrestrial locomotion
• Tetrapod
• Uniped

References

1. Melody W. Young, Edwin Dickinson, Nicholas D. Flaim and Michael C. Granatosky (2022). Overcoming a ‘forbidden phenotype’: the parrot’s head supports, propels and powers tripedal locomotion, Proceedings of the Royal Society B: Biological Sciences, 20220245, https://doi.org/10.1098/rspb.2022.0245
2. Tracy J. Thomson (2019) Three‐Legged Locomotion and the Constraints on Limb Number: Why Tripeds Don’t Have a Leg to Stand On, BioEssays 41 (10): 1900061 https://doi.org/10.1002/bies.201900061
3. Hunt, Kevin D.; Cant, John G. H.; Gebo, Daniel L.; Rose, Michael D.; Walker, Suzanne E.; Youlatos, Dionisios (1996). "Standardized descriptions of primate locomotor and postural modes". Primates. 37 (4): 363–387. doi:10.1007/BF02381373. S2CID 37235291.
4. jerry (2020-03-25). "Osteoarthritis Problems in Three Legged Dogs". Tripawds. Retrieved 2025-05-22.
5. "Frank Lentini | English version". www.franklentini.it. Retrieved 2025-05-22.