In the natural world, animals encounter terrestrial environments that range from stiff to compliant. Terrestrial locomotion across natural surfaces is highly complex, as animals must overcome substrate heterogeneity to maintain locomotor performance essential for survival (e.g., catching prey, escaping predators). Within these environments, natural substrates such as sand, gravel and cobbles, are known as granular media: a collection of discrete particles varying in material properties and behaviors when exposed to forces of different magnitude. On a single step, granular media alternates between solid and fluid-like states with potentially drastic consequences on running performance. Additionally, granular substrates at different inclinations are ubiquitous in natural environments, such as sand dunes in the desert. At the angle of repose—the maximum angle providing sand dunes their typical shape—granular media will fluidize with the slightest stress, rendering running at these angles extremely challenging. Unlike locomotion through fluids (e.g., swimming and flying), governed by the Navier-Stokes equations, how foot kinematics instigate state changes on granular media is still poorly understood, yet it is critically important for survival. The goal of my dissertation is to determine how foot use affects foot-ground interactions on granular media, with a particular focus on incline locomotion. The objectives of my dissertation are threefold: evaluate the effects of granular inclines on 1) performance and above-surface limb and foot kinematics, 2) sub-surface foot kinematics, and 3) the dynamics of foot-ground interactions using computational simulations. To fulfill these objectives, I examined three lizard species: a sand specialist (Callisaurus draconoides), a desert generalist (Crotaphytus bicinctores), and a fluid specialist (Basiliscus vittatus), selected because they have similarly shaped feet, so that differences detected among performance are due to foot kinematics rather than morphology. I ran these lizard species on a level and inclined granular trackway, while videorecording them at 500 fps using a high-speed video camera (light video) and a bi-planar high-speed fluoroscopy system (X-ray video) for the above-surface kinematics and the subsurface kinematics, respectively. Running trials were used to quantify running speed, basic stride, foot impact, and sub-surface foot kinematics, to implement on computational simulations of foot-shaped intruders entering a volume of particles to quantify force response at the particle scale. Sand specialists not only outperformed non-specialists on the incline, but maintained running speed compared to the level despite presenting some foot slip. While no significant differences across species were found for basic stride and impact kinematics, only sand specialists shifted foot intrusion angle into incline granular media to angles close to perpendicular to the substrate. At the subsurface, sand specialists maintained a stiffer foot similar to generalists, and intruded their feet shallower similar to fluid specialists. However, only sand specialists maintained toe spacings close to 6 mm on level and incline, similar to a study on intruder spacings showing peak force generation. The ground force response exhibited by the sand specialist lizard foot model revealed that by hitting the particles fast (0.7 m/s) and shallow, almost perpendicular to the substrate, toe first, with stiff feet, and toe spacings close to 6 mm, sand specialists are likely taking advantage of the inertial behavior of the particles at the angle of repose. Essentially, by paddling through the substrate’s fluid-like behaving surface, sand specialists run significantly faster than fluid specialists and generalists. My dissertation demonstrates the significance of surface and subsurface kinematics strategies to understand foot-ground interactions, especially on angled yielding substrates, contributing with knowledge to the terradynamics field and elucidating significant applications in bioengineering, bioinspiration and robotics. / Biology
| Identifer | oai:union.ndltd.org:TEMPLE/oai:scholarshare.temple.edu:20.500.12613/7204 |
| Date | January 2021 |
| Creators | Mantilla, Diana Catalina |
| Contributors | Hsieh, Tonia, Freestone, Amy, Spence, Andrew J., Flammang, Brooke E. |
| Publisher | Temple University. Libraries |
| Source Sets | Temple University |
| Language | English |
| Detected Language | English |
| Type | Thesis/Dissertation, Text |
| Format | 155 pages |
| Rights | IN COPYRIGHT- This Rights Statement can be used for an Item that is in copyright. Using this statement implies that the organization making this Item available has determined that the Item is in copyright and either is the rights-holder, has obtained permission from the rights-holder(s) to make their Work(s) available, or makes the Item available under an exception or limitation to copyright (including Fair Use) that entitles it to make the Item available., http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | http://dx.doi.org/10.34944/dspace/7183, Theses and Dissertations |
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