Natural branches vary conspicuously in their diameter, density and orientation, but how these latter two factors affect animal locomotion is poorly understood. Thus, for three species of arboreal anole lizards found on different size branches and with different limb lengths, we tested sprinting performance on cylinders with five diameters (5–100 mm) and five patterns of pegs, which simulated different branch orientations and spacing. We also tested whether the lizards preferred surfaces that enhanced their performance. The overall responses to different surfaces were similar among the three species, although the magnitude of the effects differed. All species were faster on cylinders with larger diameter and no pegs along the top. The short-limbed species was the slowest on all surfaces. Much of the variation in performance resulted from variable amounts of pausing among different surfaces and species. Lizards preferred to run along the top of cylinders, but pegs along the top of the narrow cylinders interfered with this. Pegs on top of the 100-mm diameter cylinder, however, had little effect on speed as the lizards ran quite a straight path alongside pegs without bumping into them. All three species usually chose surfaces with greater diameters and fewer pegs, but very large diameters with pegs were preferred to much smaller diameter cylinders without pegs. Our results suggest that preferring larger diameters in natural vegetation has a direct benefit for speed and an added benefit of allowing detouring around branches with little adverse effect on speed.
Supplementary material available online at http://jeb.biologists.org/cgi/content/full/215/12/2096/DC1
The study was partially supported by a grant from the National Science Foundation [IOS 0813497 to B.C.J.] and a University of Cincinnati Wieman Wendel Benedict grant to Z.M.J.
LIST OF SYMBOLS AND ABBREVIATIONS
- alternating pairs of pegs in a horizontal and vertical plane spaced every 10 cm along the primary surface
- stride frequency; inverse of the elapsed time between successive footfalls excluding pauses
- pairs of pegs in a horizontal plane spaced every 10 cm along the primary surface
- stride length; distance traveled along the long axis of the perch between successive footfalls
- no pegs
- pegs in a vertical plane spaced every 10 cm along the top of the primary surface
- pegs in a vertical plane spaced every 20 cm along the top of the primary surface
- gross speed; =40 cm divided by the total time taken to traverse this distance
- net speed; =40 cm divided by the time taken to traverse this distance excluding pausing
- average speed per stride; =fL
- © 2012.