The Effects of Surface Feature Geometry on the Propulsive Locomotion of Tree-climbing Snakes Öffentlichkeit
Lee, Michelle (Spring 2024)
Abstract
Being limbless, snakes face unique challenges when climbing trees, sometimes resorting to wrapping their bodies around the trunk to pull themselves up. However, corn snakes exhibit an alternative climbing technique that allows them to zig-zag up and down trees without wrapping. We model a large tree using a flat, vertical wall that utilizes a single vertical column of 22 force-sensitive pegs to record horizontal and vertical propulsive-force measurements as the snakes ascend or descend. On the wall, there are two types of 3 mm long pegs: the "normal" cylindrical pegs and the "tapered" pegs, which have a narrower tip, making them more difficult to grip onto. This study focuses on the force output over the body of the snakes through the combination of 3D-kinematic tracking data as well as time-resolved force data. Our findings reveal that the geometry of the pegs affects the snake's climbing ability differently when ascending versus descending. Given the probable challenges of upward climbing, the snakes were forced to utilize the tapered pegs. In these scenarios, we observed significant lateral forces exerted on the pegs, including the tapered ones, suggesting considerable effort exerted by the snakes to stabilize on the wall. On downward climbs, we observe reduced lateral forces in general, where the snakes are sometimes able to skip the tapered pegs altogether. This can indicate that downward climbs are less difficult and require less stabilizing forces. Future work will investigate how different snake species manage similar scenarios with different surface geometry.
Table of Contents
Chapter 1: Introduction 1
1.1 Motivation 1
1.1.1 Modes of Locomotion 4
1.2 Subjects of the Study: Corn Snakes 5
1.3 Goals of Thesis 6
Chapter 2: Experimental Methods 7
2.1 Experimental Setup 7
2.1.1 The Climbing Wall Setup 7
2.2 Pegs: Load Cells 11
2.2.1 Load Cell Functional Description 11
2.2.2 Precision and Accuracy of Load Cells 12
2.1.3 Peg Shape Configuration on the Wall 15
2.1.4 3D kinematic data: 16
Chapter 3: Experimental Data Collection 18
3.1 Running Climbing Trials 18
3.1.1 Modes of Snake Locomotion 18
3.1.1 Successful vs. Unsuccessful Climbs: 18
3.1.2 Upward Climbs 19
3.1.3 Downward Climbs 19
Chapter 4: Results and Discussion 20
4.1 Comparing Successful Upward with Downward Climbs 20
4.1.1 Climbing Forces and Kinematics on Upward VS. Downard Climbs 20
4.1.2 Modes of Locomotion on Upward vs. Downward Climbs 23
4.2 Comparing Successful trials with Unsuccessful trials 26
4.2.1 Forces on Segments of the Body for All Climbs 27
4.2.2 Forces on Individual Pegs for Singular Climbs 30
4.2.3 Force Histograms of Normal and Tapered Pegs for All Climbs 35
Chapter 5: Conclusion 41
5.1 Applications 41
5.2 Future Work 41
References 43
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