Locomotor characteristics of the ground‐walking chameleonBrookesia superciliaris

Abstract

Understanding the locomotor characteristics of early diverging ground‐walking chameleons (members of the genera Brookesia, Rhampholeon, Palleon, and Rieppeleon) 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. Brookesia exhibits a combination of locomotor traits, some of which are traditionally arboreal, others more terrestrial, and a few that are very unusual. Like other chameleons, Brookesia moved 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. While Brookesia exhibits 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, Brookesia often adopts an unusual footfall pattern, lateral‐sequence lateral‐couplets. Because Brookesia is 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.

Methodological Advances in Studying Postnatal Locomotor Development

“…We are in the year 2022 2023 2024, and (as if agnostic to the rise of computers) people still essentially rely on footfall patterns (Hildebrand, 1989), spatiotemporal gait parameters (stride frequency, speed, duty factor, etc. ), and visually comparing angular profiles (Ekhator et al, 2023;Jones and Hasiotis, 2023;Plocek and Dunham, 2023;Young et al, 2023b). Those are doubtlessly great methods to get an overview, and they remain the go-to first analysis for any kinematic data set.…”

“…There are numerous recent examples of studies in which spatiotemporal gait variables are the basis and (own) goal of comparison (e.g. Cheu et al, 2022;Druelle et al, 2021;Ekhator et al, 2023;Jones and Hasiotis, 2023;McHenry and Hedrick, 2023;Plocek and Dunham, 2023;Young et al, 2023b). However, it is rarely modeled how and why a study group reaches a certain speed (explanatory statistics), and the predictive power of studies on spatiotemporal variables is low (e.g.…”