MICROHABITAT USE, EFFECTS ON AGGRESSION, AND AGGRESSIVE BEHAVIOR OF RUSTY, VIRILE, AND ALLEGHENY CRAYFISH

Abstract

My research examined microhabitat utilization and competition among two invasive crayfish (Orconectes rusticus and Orconectes virilis) and one native crayfish (Orconectes obscurus) in the Monocacy River. In the field, these species utilized similar microhabitats although 0. virilis showed preference for silt. In microcosm experiments, microhabitat did not affect interspecific interactions or dominance, but 0. virilis intraspecific aggression increased in reduced cobble. In dyad trials, size-matched. 0. virilis were dominant over 0. rusticus, and 0. rusticus were dominant over 0. obscurus. In contrast, a previous study resulted in 0. rusticus dominance over 0. virilis. Orconectes virilis are larger than 0. rusticus in the Monocacy River and were dominant in laboratory trials, yet 0. rusticus is displacing 0. virilis in the field. Behavioral dominance does not appear to be directly driving the displacement of 0. virilis. Differential predation, avoidance behavior, and non-size matched encounters may influence 0. rusticus dominance in the field.