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First published online May 13, 2004
Journal of Experimental Biology 207, 2115-2131 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00995

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The effects of surface diameter and incline on the hindlimb kinematics of an arboreal lizard (Anolis sagrei)

Lawrence C. Spezzano, Jr^* and Bruce C. Jayne

Department of Biological Sciences, University of Cincinnati, PO Box 210006, Cincinnati, OH 45221-0006, USA

^* Author for correspondence at present address: Department of Zoology, Miami University, 212 Pearson Hall, Oxford, OH 45056 (e-mail: spezzalc{at}muohio.edu)

Accepted 22 March 2004

Arboreal animals often move in habitats with dense vegetation, narrow perches and variable inclines, but effects of arboreal habitat structure on locomotor function are poorly understood for most animals. Several species of Anolis lizards, which have served as a model group for relating locomotor performance to morphology, have decreased maximal sprinting speeds when perch diameter decreases. However, the effects of perch diameter on the limb movements of Anolis have not been previously studied. Hence, we quantified the hindlimb movements of Anolis sagrei, which naturally occurs on a wide variety of perch diameters and inclines. We analyzed similar speeds of steady locomotion for combinations of flat surfaces and round perches with diameters of 1, 3, 6 and 10 cm and inclines of 0° and uphill 45° and 90°. Diameter significantly affected more kinematic variables than incline, but many kinematic variables changed little with increases in diameter beyond 6 cm. As surface diameter increased, the limb posture of A. sagrei became progressively more sprawled. Significantly greater knee flexion during stance was important for locating the foot more medially during movement on narrow perches. Stride length increased and femur depression, femur retraction and long-axis femur rotation decreased significantly as the surface diameter increased. The low hip heights on the vertical incline and the narrowest perches suggest that bringing the center of mass closer to the locomotor surface is important in these circumstances for reducing the tendency to topple backwards or sideways. Most of the kinematic changes of A. sagrei with decreased perch diameter were opposite those correlated with increased speeds of locomotion for terrestrial lizards. The foot was most lateral to the hip during the swing phase and maximal lateral displacements decreased with decreased perch diameter. Consequently, the width required to accommodate limb movement also decreased as perch diameter decreased.

Key words: arboreal, locomotion, kinematics, lizard, Anolis sagrei, incline, perch diameter, limb posture

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