1Department of Anatomy and Neurobiology, Northeast Ohio Medical University (NEOMED), 2Department of Biology and Toxicology, Ashland University
Friday 8:30-8:45, Galleria North
Decades of experimental research have identified several relatively unique mechanical features of primate quadrupedalism, chief among them the habitual use of diagonal sequence (DS) gaits and hindlimb dominance in body weight support. Consensus states that such features facilitate stability on narrow and compliant arboreal substrates. The association between these locomotor features and fine-branch arboreality has been bolstered by evidence that marmosets (Callithrix jacchus) – gumnivores specialized for locomotion on broad tree-trunks – are unusual among primates, and more similar to other mammals, in showing a preference for lateral sequence gaits and forelimb dominated weight support. In this study, we further tested the links between primate quadrupedal mechanics and fine-branch arboreality by investigation the locomotion of cotton-top tamarins (Saguinus oedipus), callitrichine primates that frequently travel and forage on narrow branches, despite being morphologically quite similar to marmosets. We recorded biomechanical data from three S. oedipus (mass: 485-546 grams) moving over a horizontal 3.2cm diameter pole, examining a total of 57 walking and 110 running strides. DS gaits predominated, representing 61% and 88% of walking and running strides, respectively. Nevertheless, tamarins were primarily forelimb dominant in body weight support. Within strides, peak vertical forelimb forces exceeded peak vertical hindlimb forces by an average of 16% (peak force ratios: 0.72-1.98), and impulse ratios indicated that tamarins supported 52% of body weight on their forelimbs (range: 42-63%). Overall, these data suggest that fine-branch arboreality may be necessary, but not sufficient, to select for the suite unusual locomotor features common to most quadrupedal primates.
Funded by NSF BCS-1126760 and the NEOMED Department of Anatomy and Neurobiology.