Context-dependent agonistic response to neighbours along territory boundaries in a cichlid fish

Abstract

Abstract In many territorial animals, the level of aggression exhibited toward conspecifics depends on the magnitude of the threat they pose and/or their familiarity. We conducted aquarium experiments to investigate whether the territorial cichlid fish Julidochromis transcriptus has a context-dependent agonistic response to neighbouring conspecifics. The attacking rate of territory-holding males decreased against neighbour males in an adjacent aquarium over time but increased when stranger males replaced the neighbours in the same aquarium, indicating that males displayed the ‘dear enemy effect’ toward familiar neighbours. Females were not aggressive and the dear enemy effect was not apparent among them. Interestingly, territory-holding males also increased their attacking rate against neighbour males shifted to the opposite aquarium. Territory-holding males will modify their agonistic response to conspecific males according to the relative threat of their opponents in the context of the ‘correct-incorrect boundary paradigm’.