Approach tendency and threat display as related to social status of Siamese fighting fish,Betta splendens

Forty-eight maleBetta splendens were assigned to three groups of 16 (eight pairs) each. In two of the groups, pairs of fish were first allowed to fight until a dominance-subordinance relationship was established. Then each subject was tested on measures of time spent in approach and threat display toward either (1) its own pair member, with which it was experienced and familiar (Group EF), or toward (2) another combat-experienced fish, with which it was unfamiliar (Group EU). A third group of inexperienced and unfamiliar individuals (Group IU) were first exposed to their own mirror images and then tested for approach and threat-display duration. Pairs of these fish were then allowed to fight until dominance was determined. The three major findings were: (a) Dominant subjects approached and displayed significantly more than subordinates in all three groups; (2) Dominant subjects of Group IU did not differ significantly from dominants in the other two groups with respect to time spent in approach and display; and (3) Fish exposed to mirrors prior to combat required significantly fewer sessions to establish dominance than fish not receiving mirror exposure. Results suggest that dominant fish can be distinguished on the basis of their approach tendency and threat-display scores prior to actual physical combat. An habituation model of dominance determination was proposed.