Locomotor characteristics of the ground‐walking chameleonBrookesia superciliaris

Abstract

AbstractUnderstanding the locomotor characteristics of early diverging ground‐walking chameleons (members of the generaBrookesia, Rhampholeon, Palleon, andRieppeleon) can help to explain how their unique morphology is adapted to fit their environment and mode of life. However, nearly all quantitative studies of chameleon locomotion thus far have focused on the larger “true arboreal” chameleons. We investigated kinematics and spatiotemporal gait characteristics of the Brown Leaf Chameleon (Brookesia superciliaris)on different substrates and compared them with true arboreal chameleons, nonchameleon lizards, and other small arboreal animals.Brookesiaexhibits a combination of locomotor traits, some of which are traditionally arboreal, others more terrestrial, and a few that are very unusual. Like other chameleons,Brookesiamoved more slowly on narrow dowels than on broad planks (simulating arboreal and terrestrial substrates, respectively), and its speed was primarily regulated by stride frequency rather than stride length. WhileBrookesiaexhibits the traditionally arboreal trait of a high degree of humeral protraction at the beginning of stance, unlike most arboreal tetrapods, it uses smaller shoulder and hip excursions on narrower substrates, possibly reflecting its more terrestrial habits. When moving at very slow speeds,Brookesiaoften adopts an unusual footfall pattern, lateral‐sequence lateral‐couplets. BecauseBrookesiais a member of one of the earliest‐diverging groups of chameleons, its locomotion may provide a good model for an intermediate stage in the evolution of arboreal chameleons. Thus, the transition to a fully arboreal way of life in “true arboreal” chameleons may have involved changes in spatiotemporal and kinematic characteristics as well as morphology.