Aggressive Behaviours of Territorial Cichlid Fishes against Larger Heterospecific Intruders

Abstract

Aggressive behaviours at nesting territories of cichlid fishes were observed in Lake Tanganyika. Subject fishes were Neolamprologus toae, Tropheus moorii, Ophthalmotilapia nasutus, Limnotilapia dardennii and Petrochromis polyodon. They attacked and repelled various sized heterospecific fishes from the territories. Against much larger intruders, the fishes quickly approached and pecked them. The larger fishes never conducted counter-attack, and left the territories. Such pecking behaviour was regarded as a kind of attack, but greatly different from attacks in interspecific territorialities of cichlids reported hitherto, which are usually organized in size-dependent dominance relationships. This paper discusses the domination of the nesting territory owners in a context of `symmetry' of territoriality.