Crayfishes belonging to the family Cambaridae occur in two adult male morphs, Form I which is reproductively competent and Form II which is nonreproductive. In our first experiment, we compared the behavior of Form I and Form II animals by measuring walking, sheltering, feeding, and attraction to a female conspecific in single male Orconectes rusticus. Our data demonstrated that, under laboratory conditions, Form II animals spent significantly more time in shelters than did Form I animals. The two forms did not differ significantly in the other measured behaviors. In our second experiment, we examined agonistic behavior in males of each form. When placed in intraform groups of four animals, Form II crayfish displayed fewer agonistic acts and spent less time fighting than did Form I males. In Form II males, increased sheltering may serve to reduce the risk of predation, and fewer agonistic acts may reflect a lower motivation to compete with other males.