Fight, fatigue, and flight: narrowing of attention to a threat compensates for decreased anti-predator vigilance

Abstract

Fighting carries predation risk because animals have limited attention, constraining their ability to simultaneously engage in aggression and anti-predator vigilance. However, the influence of interspecific aggression and fatigue on the predation cost of fighting is seldom examined, although both are unignorable aspects of fighting. Here, I incorporated both factors in a series of field experiments on the cichlid Lamprologus ocellatus. If territorial males respond more strongly to conspecific territorial intruders than heterospecific intruders, then they should delay escape more frequently during intraspecific fighting than interspecific fighting. Consequently, although I predict that vigilance would be decreased as fighting progresses in both fighting, intraspecific aggression should decrease vigilance more than interspecific aggression. Males were also exposed to a predator approaching at different (slow or fast) speeds during these fighting bouts. Delays in predator detection and flight initiation were quantified and these predictions were tested. As predicted, males were responded more strongly to intraspecific intruders, resulting in slower predator detection and fleeing times than when encountering interspecific intruders. Furthermore, flight latency decreased with increasing fight duration, suggesting that fatigue negatively influenced escape responses. However, contrary to prediction, the vigilance decrement rate was faster in response to slow predators than to rapid predators, and was not influenced by intruder identity. This suggests that fighting males reserve their attention for information critical to their survival and are less vigilant toward a less-threatening (slow approaching) predator. This cognitive allocation may be an adaptive compensation for fatigue-related low vigilance during fighting.