The cantilever abilities of snakes

We quantified the abilities of snakes to extend the anterior body horizonta lly without support, and we evaluated data for 31 species representing five families. Generally, terrestrial snakes exhibit rather uniform cantilever ability and can extend the body 30-50% of total body length. Arboreal speci es exhibit statistically superior performance both within and among familie s, with some species extending the body to more than 50% of body length. Ex treme divergence of cantilever abilities occurs between arboreal and aquati c species. Intraspecific comparisons also show that juvenile snakes cantile ver better than adults, presumably due to a lower mass relative to body len gth. Musculoskeletal features of the vertebral column are generally conserv ed in evolutionary terms, thus possibly explaining the generally uniform ca ntilever abilities in large numbers of snake species. However, several modi fications of vertebrae and associated epaxial muscles and their tendons app ear to be related to cantilever performance.