Social responsiveness and physical space as determinants of agonistic behavior inBetta splendens

Two experiments examined the conditions under whichBetta agonistic responding occurs by manipulating physical space and the species and social responsiveness of an opponent. In Experiment 1, both the species (conspecific or nonconspecific) and the aggressiveness (aggressive or nonaggressive) of the opponent were manipulated. The results indicated that agonistic behavior was greater with both conspecifics and aggressive opponents. Experiment 2 examined the effects of physical space and social responsiveness of the opponent on intraspecific aggressive behavior. An inverse relationship was found between physical space and the number of attacks directed toward the opponent. The results of both experiments also indicated thatBetta tend to attack aggressive opponents more than nonaggressive ones. It is suggested thatBetta aggress either when the individual animal is threatened or when physical space is limited.