Effects of ontogeny and odors on behavior: The influence of crayfish size and fish odors on crayfish movement

Intrinsic and extrinsic factors interact in complex ways to influence indiv idual behavior. We characterized how ontogenetic stage and chemicals from p otential predators influence nocturnal movement of Orconectes virilis befor e and during exposure to chemicals from rock bass, yellow perch, darters, a nd 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 cray fish behavior. Our results corroborate other studies showing that predator odors alone do nor change the short-term activity patterns of O. virilis. B ecause 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 o f animals without altering behavior).