Meeting Abstract
Burrowing is a widely-used strategy for the survival of many groups of animals, but is particularly important for rodents. To study this essential behavior, we used 3D x-ray to measure burrowing kinematics and the Tunnel-Tube 3.0 to measure 3D burrowing dynamics. Here, we present the first complete 3D analysis of burrowing biomechanics in a vertebrate. Lessons from our earlier designs have led to the modular, streamlined Tunnel-Tube 3.0: Two interchangeable plastic tubes arranged in series and mounted on an ATI nano-17 6-axis load cell. The tube through which the animal enters is empty and aligned with a second, substrate-filled tube. The substrate-filled tubes are uniformly packed and can be exchanged between trials, allowing for a more consistent substrate over time. The dual-tube design allows us to measure forces produced by the animal’s fore- and hindlimbs independently. Botta’s pocket gophers (Thomomys bottae) are subterranean rodents which spend the majority of their lives underground, thus making them ideal test subjects for studies of burrowing biomechanics. Pocket gophers burrowed in four substrate conditions in order to assess the effects of substrate hardness and composition on burrowing mechanics. Substrate conditions included: Soft radiolucent substrate, hard radiolucent substrate, soft natural soil, and hard natural soil. Radiolucent substrates were made up of walnut shells and coconut fiber; Natural soils were collected from trapping sites. In soft substrates, pocket gophers exhibited scratch-digging, using the forelimbs to loosen and remove the substrate. In hard substrates, pocket gophers exhibited both chisel-tooth and scratch-digging, typically using the teeth to penetrate the hard substrate and the forelimbs to remove loosened substrate. Pocket gophers produced greatest force when using chisel-tooth methods in hard substrates.
