Ecomorphological correlates of grasping forces in strepsirrhine primates

Powerful digital grasping is essential for primates navigating arboreal environments and is often regarded as a defining characteristic of the order. However, in vivo data on primate grip strength are limited. In this study, we collected grasping data from the hands and feet of eleven strepsirrhine species to assess how ecomorphological variables-such as autopodial shape, laterality, body mass and locomotor mode-influence grasping performance. Additionally, we derived anatomical estimates of grip force from cadaveric material to determine whether in vivo and ex vivo grip strength measurements follow similar scaling relationships and how they correlate. Results show that both in vivo and anatomical grip strength scale positively with body mass, though anatomical measures may overestimate in vivo performance. Species with wider autopodia tend to exhibit higher grip forces, and forelimb grip forces exceed those of the hindlimbs. No lateralization in grip strength was observed. While strepsirrhine grip forces relative to their body weight are comparable to those of other primates and slightly exceed those of humans, they are not exceptional compared to other arboreal mammals or birds, suggesting that claims of extraordinary primate grasping abilities require further investigation.