Right-sided bias in fallow deer terminating parallel walks: evidence for lateralization during a lateral display

Lateral displays during agonistic interactions are assumed to provide contestants the opportunity to assess the opponent’s quality. Once an individual has acquired sufficient information, a decision to terminate the display can be made and either escalation to fighting or de-escalation and movement away from the opponent occurs. Because cerebral lateralization enhances the processing of complex cognitive tasks in the visual domain, it is possible that lateralization might provide an efficient means by which an assessment of the opponentʹs quality is facilitated. I investigated whether there is evidence for lateralization in the decision to terminate parallel walks during fights recorded between individually identifiable male fallow deer, Dama dama. Males exhibited a significant bias to terminate parallel walks when displaying their right flank over their left; therefore, the decision to end a parallel walk showed evidence for lateralization. There was an increasing tendency to show a right-sided bias when terminating the parallel walk as body length increased and heavier males terminated parallel walks sooner than lighter males. Therefore, larger individuals displayed a greater tendency towards lateralization than smaller individuals. Moreover, lighter males showed a greater tendency to escalate parallel walks to fighting. These results show evidence for lateralization in the decision to terminate lateral displays during escalated contests in an ungulate species, and suggest that lateralization provides a mechanism by which contestants can resolve contests at a low cost.