The Effects of Speed on Terrestrial Locomotor Kinematics in the Common Garter Snake (Thamnophis sirtalis)

• Main Author: Bulla, Andrew J
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01.01.2013
• Subjects: Biology; Biomechanics; Zoology
• ISBN: 1303701979; 9781303701979

Movement presents a unique challenge for snakes (suborder Serpentes), which utilize limbless locomotion to move in terrestrial and aquatic environments. Lateral undulation, the fastest and most commonly used type of snake locomotion, has been extensively studied in both contexts due to its prevalence in the animal kingdom. However, the effects of speed on locomotor kinematics have only been studied in aquatic conditions. During swimming, snakes are known to increase speed by increasing wavelength and amplitude while maintaining constant frequency. Additionally, amplitude in aquatic environments increases from the anterior to the posterior regions of the body. The mechanism for increasing speed in a terrestrial context is unknown, despite the fact that the majority of snakes reside in terrestrial areas. Therefore, I compared terrestrial locomotor kinematic data with existing aquatic swimming data to determine whether kinematic differences exist for increasing speed in different environments. In this study, Eastern Garter Snakes, Thamnophis sirtalis (n=4), were filmed utilizing lateral undulation at two different speeds with 120fps high-speed video. I examined speed effects on locomotion by conducting detailed comparisons of key kinematic and performance variables including wavelength, amplitude, frequency and segmental angles of the waves created during lateral undulation. The speed effects of terrestrial locomotion were found to differ from aquatic locomotor pattern in wavelength; the mean wavelength observed in our terrestrial trials increased significantly as speed increased. Other variables, including frequency, amplitude and growth of amplitude from head to tail, exhibited similar patterns to aquatic locomotion. This study provides insight into the mechanisms by which snakes generate locomotor complexity from a simple body plan.