Comparative biomechanical analysis of jumping between the arboreal northern treeshrew ( <i>Tupaia belangeri</i> ) and the fat-tailed dwarf lemur ( <i>Cheirogaleus medius</i> )

Abstract Jumping allows arboreal mammals to navigate disparate canopy supports. Existing research suggests that the long, mobile limbs of many small primates—including basal primate ancestors—facilitate arboreal jumping performance by extending centre of mass (CoM) excursion during push-off, while reducing forces applied to the support to potentially improve stability on narrow, compliant branches. We test this premise using force platform and micro-CT analyses to compare the biomechanical strategies and corresponding body morphology modulating vertical jumping performance in Cheirogaleus medius (N = 3), a small arboreal primate, and Tupaia belangeri (N = 3), a similarly-sized semi-arboreal/terrestrial treeshrew (close relative to primates). As predicted, to increase take-off velocity (the primary determinant of jump height), T. belangeri prioritized force production and high mechanical power. This power-focused strategy corresponds with larger attachments and longer moment arms for hip and knee extensors. In contrast, C. medius prioritized CoM excursion over a longer push-off duration, a strategy enabled by their greater hip joint mobility. The ability to minimize force production in C. medius supports hypotheses of frequent use of narrow, compliant supports during early primate evolution, allowing early primates to jump more effectively and safely in a small branch milieu.