Mechanical Constraints during Vertical Climbing Reveals Limited Deviation from Theoretical Minima

Area of Science:

• Biomechanics
• Locomotion
• Functional Morphology

Background:

• Center of mass (COM) mechanics are crucial for understanding locomotion energetics.
• Previous studies on COM mechanics have largely neglected climbing scenarios.
• Interspecific variation in anatomy and locomotion strategies necessitates a broader investigation into climbing costs.

Purpose of the Study:

• To investigate three-dimensional COM movements during climbing across diverse species.
• To test theoretical expectations of climbing costs and the impact of interspecific variation.
• To determine the influence of out-of-plane COM movements and inclination angles on climbing costs.

Main Methods:

• Analysis of 3D COM movements in five phylogenetically distinct species during climbing.
• Comparison of climbing costs across species with varying limb numbers, adhesion mechanisms, body masses, and postures.
• Experimentation with rosy-faced lovebirds to assess the effect of inclination angle on COM mechanical energy.

Main Results:

• Potential energy is the primary driver of total mechanical costs during climbing, exceeding kinetic energy contributions.
• Out-of-plane COM kinematics have a negligible impact on overall locomotor costs.
• Inclination angle has minimal effect, as potential energy accumulation rapidly increases with substrate steepness.

Conclusions:

• Climbing costs are universally dominated by potential energy, irrespective of species-specific anatomical or behavioral traits.
• There is a lack of clear evidence for specialized anatomical or behavioral adaptations enhancing climbing efficiency across the studied species.
• The findings highlight universal mechanical challenges in scaling vertical substrates, informing studies of climbing in extant and fossil taxa.