Meeting Abstract

24-3  Thursday, Jan. 5 10:45 - 11:00  How the biomechanics of ricochetal bipedalism enhances predator evasion, resource partitioning, and taxonomic diversity in desert rodent communities MOORE, TY*; COOPER, KL; BIEWENER, AA; VASUDEVAN, R; Univ. of Michigan; Univ. of California, San Diego; Harvard Univ.; Univ. of Michigan taliaym@gmail.com http://sites.google.com/site/taliayukimoore

Bipedal hopping in kangaroos is highly economical, enabling foraging over large areas; however, small bipedal rodents differ vastly in their biomechanics and ecology. We characterized the gait, dynamics, kinematics, and behavioral ecology of jerboas, small bipedal desert rodents. Jerboas are the only bipedal rodent with three gaits, which we found are not used in distinct speed ranges as would be expected for most terrestrial animals (p=0.07). Gaits are instead associated with distinct ranges of acceleration and deceleration (p=0.02), and jerboas frequently transition between gaits during short bouts of locomotion. Furthermore, we found that jerboa tendon elastic energy storage contributes only 6% of the energy required for a vertical leap, suggesting specialization for acceleration and maneuverability. By simulating predation under natural field conditions, we found that jerboas use their enhanced maneuverability to generate significantly less predictable trajectories than sympatric quadrupedal rodents, likely limiting a predator’s ability to plot an intercept course. Therefore, jerboas should be able to forage in areas exposed to predation with less risk than sympatric quadrupeds. We tested this hypothesis by measuring open-field anxiety in field and lab conditions and found that jerboas spend over 300% more time in exposed areas than sympatric quadrupedal jirds (p=0.00016). The enhanced maneuverability and predator evasion ability conferred by ricochetal bipedalism therefore appears to underlie the distinct habitat preferences of sympatric rodent species, decreasing interspecific competition. Thus, evolutionary innovation in locomotor biomechanics helps to explain the surprisingly diverse rodent communities competing for limited desert resources.