Meeting Abstract

17.4  Saturday, Jan. 4 11:15  The Effects of Substrate on the Bipedal Hopping of Kangaroo Rats ECKWRIGHT, MJ*; MCGOWAN, CP; SHELLOOE, L; University of Idaho; University of Idaho; Gonzaga University eckw7684@vandals.uidaho.edu

In the wild, animals live on a wide variety of substrates including sand, snow, leaf-litter, and so on. These various substrates exhibit a wide range of physical properties that can affect locomotion, and many animals have evolved specialized forms of locomotion to better navigate their native substrate. Despite the large role that substrate plays, most studies done on human and animal locomotion have used solely rigid substrates. The few studies that have involved varied substrates have focused mostly on humans on elastic surfaces, though natural substrates are more likely to be dampers. There have also been numerous studies done with desert lizards on sand, but this is only one particular case. For our study, we focused on the desert kangaroo rat, which is a sand-native bipedal hopper. We recorded the kangaroo rats hopping over a rigid substrate with 0, 1, 2, and 3 cm of sand overlain. We used video and force data to calculate the leg stiffness and vertical stiffness for each trial. The results were vertical stiffness values that increased with the addition of sand, but not between sand levels. Leg stiffness values were independent of sand level. These results suggest that desert kangaroo rats increase their vertical stiffness on sand, possibly to make up for the energy lost to the substrate.