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Testing mechanisms for weight support distribution during inverted quadrupedalism in primates
Edwin Dickinson1, Melody W Young1, Michael C Granatosky1,2
1Department of Anatomy, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York, USA.
Summary
Primates exhibit unique inverted quadrupedal locomotion, shifting weight support to forelimbs and increasing joint movement. This suggests a facultative use of basal neuromuscular traits for this infrequent arboreal behavior.
Area of Science:
- Primate locomotion
- Comparative biomechanics
- Arboreal adaptations
Background:
- Primates display hindlimb-biased weight support during above-branch locomotion, unlike most mammals.
- Inverted quadrupedalism, where primates hang beneath branches, is observed in over 50 primate taxa.
- This inverted gait involves forelimb-biased weight distribution, potentially protecting hindlimbs from tensile loading.
Purpose of the Study:
- To compare kinetic and kinematic data of upright and inverted quadrupedalism in select primate species.
- To contrast primate inverted quadrupedalism with the locomotion of the two-toed sloth.
- To investigate the biomechanical differences between primate arboreal locomotor modes.
Main Methods:
- Kinetic and kinematic data collection during upright and inverted quadrupedalism.
- Comparative analysis across four primate species (Lemur catta, Varecia variegata, Cebus capucinus, Saimiri sciureus).
- Reference against data from the two-toed sloth (Choloepus didactylus) as a model.
Main Results:
- Inverted quadrupedalism in primates shows increased forelimb weight support and contact times compared to above-branch locomotion.
- Greater forelimb and hindlimb joint excursions are observed during inverted quadrupedalism.
- Established biomechanical models for upright walking do not accurately predict inverted locomotion.
Conclusions:
- Inverted primate quadrupedalism is biomechanically distinct from above-branch locomotion.
- Primates may utilize fundamental neuromuscular gait characteristics for inverted locomotion.
- This behavior appears to be a facultative adaptation rather than a specialized, continuously employed gait.
