The role of the vertebral column during jumping in quadrupedal mammals

Graduation date: 2010Little, if any, quantifications have been made on the contribution of the vertebral column during jumping in quadrupedal mammals. Previous studies of jumpers have focused on the morphological and physiological specializations of the hindlimbs. In this study, such specialization was measured during the supramaximal jumps of the Pacific jumping mouse (Zapus trinotatus), whose peak of jump power occurs late during ground contact time, indicating the use of elastic mechanisms in the hindlimbs. However, since contribution by back muscles during jumping Zapus could not be ruled out, a second study measured the actual work contribution of the back muscles during standing vertical jumps in domestic cats to be 51-62% of total body work, increasing with jump height. In addition, the peak of back power was measured a mean 14% of contact time prior to the onset of hindlimb power, suggesting the back provides an additive effect on ground reaction forces and stressing the importance of the relative timing of various musculoskeletal elements in jumping movements. Extending the role of the vertebral column during jumping to a larger ecological view, specimens of extant canids and felids were measured for basic morphological differences in their postcranial skeletons to explain fundamental differences in hunting technique. As two distinct evolutionary lineages within the Order Carnivora, most canids are cursorial pursuit predators, while felids typically are ambush hunters who employ a pouncing locomotory technique. Skeletal length ratios were found to be significantly higher on average in canids than in felids for the forelimb-to-thoracolumbar vertebrae, forelimb-to-hindlimb, metatarsal-to-femur, humerus-to-femur, and radius-to-femur. Neural process heights for the T10 to L5 vertebrae (adjusted for scaling effects) were significantly taller on average in canids and angles of the post-anticlinal vertebrae were oriented more caudally in canids than in felids. Canids tended to have wider pelvises than felids, though no significant difference was found between pelvis-to-femur or ilium-to-pelvis length ratios. These studies provide further insight into the integrated nature of the musculoskeletal system during jumping and give evidence that jumping locomotion as manifested in hunting style is influenced by basic morphological differences between extant canids and felids