Fighting behaviour, vigilance and predation risk in the cichlid fish Nannacara anomala

I studied the fighting behaviour of a small South American cichlid fish, Nannacara anomala, in relation to predation risk. In this species,which reduces vigilance during escalated fighting, differences in fighting ability are most accurately assessed during mouth wrestling. Thus, there is a potential trade-off between agonistic behaviours that are effective for assessing differences in fighting ability between contestants and agonistic behaviours that minimize the risk of being killed by predators. I investigated whether breaks between bouts of mouth wrestling improved the contestants' ability to flee from an approaching model fish predator. During the breaks-between mouth wrestling the contestants had a significantly longer escape distance than males that were actively mouth wrestling. Fighting males also changed their fighting behaviour after the introduction of the model predator compared with males that were not exposed to it. Low-intensity behaviours such as lateral display and tail beating were preferred to mouth wrestling. In addition, both the number and duration of bouts of active mouth wrestling decreased significantly after the introduction of the model predator while the duration of the breaks between bouts of active mouth wrestling increased significantly compared with the control. Including predation risk in the costs of intense fighting may increase our understanding of both the temporal structuring of fighting behaviour and the evolution of fighting behaviour in general. (C) 1998 Th Association for the Study of Animal Behaviour.