Meeting Abstract
57.5 Jan. 6 Effects of perch diameter and incline on the arboreal locomotion of snakes ASTLEY, H. C.*; JAYNE, B. C.; Univ. of Cincinnati; Univ. of Cincinnati astleyhc@email.uc.edu
Moving in arboreal habitats poses several functional challenges including variable branch diameters, inclines, grasping, balancing and fitting onto the limited width of the perch. In contrast to lizards and primates, the arboreal locomotion of snakes is poorly understood despite the fact that many snake species are arboreal. Thus, to determine how perch diameter and incline affect the kinematics and locomotor performance of snakes, we videotaped one-meter long corn snakes (Elaphe guttata) moving on seven cylinders (diameters 1.6 – 20 cm) at five inclines (horizontal, +45� and +90�). Many of the effects of diameter depended on incline. For example, snakes could not move uphill or downhill on the two largest perch diameters. When moving downhill, snakes often slid continuously while grasping the perch to reduce speed. Unlike downhill locomotion, horizontal and uphill movement was a variant of concertina locomotion, in which the snake formed alternating bends of the body that periodically stopped and grasped the perch. For a given diameter, the average forward velocities were greatest, intermediate and slowest when moving downhill, horizontally and uphill, respectively. When moving horizontally, the forward displacement per cycle had large and significant increases with increased diameter, but differences in forward velocity were minimal as a result of increased cycle duration. Similar to the manner in which snakes fit into tunnels of varying width, as perch diameter increased the corn snakes had fewer lateral bends of the body and the angle of the snake�s body between the left and right sides of the perch increased and approached ninety degrees. The detrimental effects of inclined large diameter perches on the locomotion of corn snakes resemble those of some primates, but they contrast with the beneficial effects for most arboreal Anolis lizards, which can adhere to perches without grasping them.
