Differences in behavioral responses of an invasive crayfish (O. rusticus), and a native crayfish (O. virilis), in the presence of a large predator (Micropterus dolomieui).

Abstract

The native crayfish species Orconectes virilis is being displaced significantly by the introduced species Oroconectes rusticus. The mechanism of this displacement is of importance to ecologists predicting the future effects of O. rusticus on native aquatic communities. In this study, individual crayfish of each species were placed in direct contact with a large predator. Differences in behavioral responses including time sppent in shelter vs. not, time spent in threat posture, number of strikes by crayfish, and number of strikes by bass were recorded. Data revealed no significant difference in the time spent in shelter by either species. Likewise, no differences in time spent in threat posture, or number of strikes by either crayfish or bass was observed based on the data collected. The native O. virilis suffered 6 fatalities throughout the duration of the study, while O. rusticus suffered only 1 fatality. These findings suggest that differences in behavioral response to the presence of a predator are not a strong mechanism of displacement.