Intrinsic and extrinsic factors interact in complex ways to influence individual behavior. We characterized how ontogenetic stage and chemicals from potential predators influence nocturnal movement of Orconectes virilis before and during exposure to chemicals from rock bass, yellow perch, darters, and a control. Smaller crayfish spent more time moving and moved faster than larger individuals. Fish odor did not alter the short-term movement rates of crayfish. Thus, intrinsic factors such as individual size influence crayfish behavior. Our results corroborate other studies showing that predator odors alone do not change the short-term activity patterns of O. virilis. Because studies have established that O. virilis can detect these odors and shift their activity when predators are present, we suggest that odor cues may function as primers (i.e., stimuli that change the motivational state of animals without altering behavior).