Mechanical Constraints during Vertical Climbing Reveals Limited Deviation from Theoretical Minima.

This article investigates the mechanics of center of mass (COM) movements and associated mechanical energy costs during climbing across five phylogenetically diverse species, including humans (Homo sapiens), rosy-faced lovebirds (Agapornis roseicollis), Madagascar hissing cockroaches (Gromphadorhina portentosa), Australian tree frogs (Ranoidea caerulea), and common house geckos (Hemidactylus frenatus). The study finds that climbing costs are overwhelmingly dominated by potential energy related to vertical displacement, with kinetic energy—both in-plane and out-of-plane—contributing minimally regardless of limb number, posture, adhesion mechanisms, or body mass (ranging from 0.008 to 84 kg). Inclination angle changes and out-of-plane COM movements have little effect on overall mechanical costs, and climbing efficiency is primarily influenced by minimizing mediolateral and normal excursions rather than anatomical or behavioral adaptations. These results suggest that mechanical demands of climbing impose universal energetic constraints across taxa and caution against inferring specialized climbing adaptations solely from morphology, especially in fossil species.