The responses of individually housed crayfish (Orconectes virilis) were recorded during introduction of water from aquaria containing disturbed or undisturbed animals. When female O. virilis were disturbed, form II males assumed low-level alert postures significantly more than when those females were undisturbed. Similar results were obtained when the source animals were female Cambarus diogenes, a sympatric crayfish. When the newt Notopthalmus viridescens was disturbed, the crayfish responses were strong but resembled stress behavior. The responses by crayfish to disturbed vs. undisturbed catfish (Ictalurus natalis) were not significantly different.