Behavior and morphology are adaptations to foraging in physically demanding and risky habitats. At the crux of behavior and morphology, locomotion is an adaptation that hypothetically facilitates niche partitioning and competition in vertebrate communities. And how fast an animal chooses to move has physiological and ecological consequences. We investigate speed choice and locomotor behavior of kangaroo rats (Dipodomys nelsoni n=10, D. merriami n=10) under varying risk manipulations at the Mapimí Biosphere Reserve, Durango, México. Specifically, we test the hypothesis that changes in terrain will increase perceived foraging risk, thereby altering behavior. Second, we predicted that a waning moon will decrease the perceived risk. Locomotion and behavior were measured from video recordings (30 Hz) as individuals foraged under semi-natural conditions. We used rocks representative of nearby habitats to manipulate terrain. We chose these rocks because they delineate D. nelsoni habitat. Individuals of this species are denizens of flat, sandy areas. Preliminary data suggest kangaroo rats do not alter their locomotor behavior or speed relative to moonlight. Observations include a reluctance to approach manipulated substrate conditions by D. nelsoni, but not D. merriami. Accelerations, turns, and jumps were observed during interspecific competitions. Speeds were as high as 6 ms^-1 during interspecific chases but were slower (~3 ms^-1) during baseline activity. We discuss our results in the context of bipedal hopping, habitat use, and mechanisms of species coexistence. Sponsored by a Company of Biologists Travelling Fellowship 180221 to CEC.