Meeting Abstract
The study of burrowing biomechanics has been largely restricted to kinematics and one-dimensional force analyses in unnatural, soil free environments. We introduce the Tunnel-tube 2.0, a reworking of our previous force-sensitive tunnel-tube. This tube is composed of two custom designed and 3D-printed ABS plastic tube halves. The first half serves as an entry-tube leading to a soil-filled tunnel-tube. This second half consists of a thin-walled rubber tube covered with an array of x-ray markers and sealed inside of an oversized ABS plastic tube. The x-ray markers change position as the animal presses against the soil inside of the rubber tube, allowing us to track the direction in which outward force is applied to the soil during burrowing. A pressure transducer monitors the air in the inter-tube space between the thin-walled rubber tube and rigid ABS tube to determine the magnitude of outward force applied to the soil during burrowing. Each half of the tube is mounted on a separate six-axis force-torque transducer (ATI nano-17) six-axis load cell that measures the net reaction force exerted on the animal. During burrowing, the entry tube measures reaction forces on the hind limbs, while the soil-filled tunnel tube measures reaction forces on the forelimbs. With the exception of body weight support, reaction force must be equal and opposite in the entry-tube and tunnel-tube. In contrast, reaction moments about the transducers of the entry-tube and tunnel-tube provide information about the point of application of force for the hind- and forelimbs during burrowing. We use Tunnel-tube 2.0 to measure the burrowing of Merriam’s kangaroo rats (Dipodomys merriami), which are known to dig extensive burrows, and we elucidate some mechanisms of burrowing in this species.
