Behavioural persistence during an agonistic encounter differentiates winners from losers in green anole lizards

Abstract

Agonistic encounters featuring ritualized displays precede the establishment of dominance relationships in many animals. We investigated the predictive value of the amount of display behaviour (number and duration of displays) vs. quickness to display (latency to express a display behaviour) in determining the outcome of aggressive interactions and establishment of dominant vs. subordinate status in male green anole lizards, Anolis carolinensis. Similar-sized males were paired and observed for ninety minutes as they established social status. We recorded the number, duration (where appropriate) and latencies to first expression for multiple behavioural display components (head bob A, B and C, dewlap displays, open mouth displays, pushups, lateral displays) and colour changes (eyespot presence and body colour changes). Males that eventually won and became the dominant male had significantly higher counts and durations with the exception of Bob C counts, pushup counts and open mouth duration. Future dominants also maintained a green body colour longer than future subordinates, which had brown shades more often and for longer durations. Latency to first express a display component was shorter in future dominants for head bobs A and C, dewlap and open mouth displays when all data were considered. However, all significant latency differences disappeared when data only from pairs in which both males displayed a behaviour were included in the analysis. Counts, durations, and latencies were highly correlated with each other within individuals. The results indicate that behavioural display patterns during an initial display contest predict the outcome of the interaction, with the amount of display behaviour being the best predictor of whether a male will win or lose the contest and hence become dominant or subordinate. These results are consistent with the idea that displays are honest signals of a male’s physiological capacity or stamina, and hence fighting and resource holding ability.