Predator avoidance strategies of the crayfish Orconectes virilis

Field experiments compared the chemically-mediated responses of the crayfish Orconectes virilis and O. propinquus to food stimuli, alarm substance, disturbance chemicals and a combination of food and alarm. The combination of alarm and food stimuli resulted in a very marked decrease in the number of O. virilis attending a site compared to the food stimulus alone. There were also differences between the disturbance and alarm responses of O. virilis with individuals spending less time near sources of alarm substance as compared to sources of disturbance chemicals. Individuals of O. propinquus showed no differences in responses to the experimental treatments. Variations in the level of activity were consistent with lunar cycle of activity in O. virilis, with the greatest activity near new moon, and the least near full moon.