Effects of load on locomotion in the brown anole, Anolis sagrei

Abstract

Locomotion is a crucial means of predator escape, foraging, and social interactions in many animals, and the ability of an animal to excel in this performance will have a direct impact on its overall fitness (Arnold 1983, Wainwright 1994). A factor that may hinder performance is the addition of a load such as a large meal or clutch of eggs, which is a challenge many species must face. Locomotor performance may also be largely dependent on sex, size, or a combination thereof (Losos 1990, Irschick and Garland 2001). Selective pressures related to those factors often result in adaptations in morphology or behavior associated with maximal performance capabilities (Cullem 1998, Van Damme et al 2008). Examining locomotor performance and understanding the associated adaptations can allow us to draw conclusions about fitness (Arnold 1983, Husak and Fox 2008). The present study was designed to determine the effects of increased load on running and jumping performance in the lizard Anolis sagrei. For running, maximum velocity was examined because of its ecological importance in many lizard species; short bursts of speed close to maximal capacity are used to evade predation (Van Damme et al 2008). Gait patterns were also explored, as these have been known to change to compensate for a locomotor challenge (Irschick et al 2003). Jump distance, take-off velocity, jump angle, and power output will be examined in jumping, which is another common form of movement in anoles. It was found that performance in both areas of locomotion declined under added load, and kinematics such as stride length and take-off velocity were altered as well, but females outperformed males relative to size in both running and jumping--a rarely reported occurrence.