Alcohol, habituation and the patterning of aggressive responses in a cichlid fish.

Territorial cichlids were presented for 30 min with a conspecific male intruder (contained in a clear glass tube). Eight hr prior, 2 groups were administered alcohol (0.15 or 0.30 percent in the aquaria water). A third group served as a control. Three responses were recorded to allow analysis of topographic changes in behavior as well as changes in absolute levels. During the habituation phase, the normal group showed a sequence of long displays, followed by shorter ones as the frequency of attacks increased. The occurrence of threat which gradually gives way to attack is characteristic of the agonistic behavior of this species. In contrast to the controls, the 0.15 percent group was hyperaggressive, while the 0.30 percent group was hypoaggressive. Furthermore, the patterning of responses were abnormal. The 0.15 percent group gave abbreviated threats and more attacks (interpreted as a tendency to attack without warning); whereas, the 0.30 percent group gave many long threat displays, but few attacks. A stimulus specificity test provided strong evidence that the waning found during the initial phase was habituation.