Search for: All records

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. 

ABSTRACT Jumping is a crucial behavior in fitness-critical activities including locomotion, resource acquisition, courtship displays and predator avoidance. In primates, paleontological evidence suggests selection for enhanced jumping ability during their early evolution. However, our interpretation of the fossil record remains limited, as no studies have explicitly linked levels of jumping performance with interspecific skeletal variation. We used force platform analyses to generate biomechanical data on maximal jumping performance in three genera of callitrichine monkeys falling along a continuum of jumping propensity: Callimico (relatively high propensity jumper), Saguinus (intermediate jumping propensity) and Callithrix (relatively low propensity jumper). Individuals performed vertical jumps to perches of increasing height within a custom-built tower. We coupled performance data with high-resolution micro-CT data quantifying bony features thought to reflect jumping ability. Levels of maximal performance between species – e.g. maximal take-off velocity of the center of mass (CoM) – parallel established gradients of jumping propensity. Both biomechanical analysis of jumping performance determinants (e.g. CoM displacement, maximal force production and peak mechanical power during push-off) and multivariate analyses of bony hindlimb morphology highlight different mechanical strategies among taxa. For instance, Callimico, which has relatively long hindlimbs, followed a strategy of fully extending of the limbs to maximize CoM displacement – rather than force production – during push-off. In contrast, relatively shorter-limbed Callithrix depended mostly on relatively high push-off forces. Overall, these results suggest that leaping performance is at least partially associated with correlated anatomical and behavioral adaptations, suggesting the possibility of improving inferences about performance in the fossil record.