Individuals often display a preference for one side of their body during aggressive encounters. This may be a lateralized preference for using one structure of a bilateral trait during display or physical attack, or for keeping the opponent in one visual field. Alternatively, it may be the case that behavioural lateralization and the degree of symmetry expressed by bilateral structures are correlated forms of developmental instability. We examined whether there was an association between lateralization during a lateral display and different measurements of antler size and symmetry (beam length, beam circumference, brow tine length and coronet circumference). Three models addressed different structural measures: the right antler, the larger antler and antler symmetry. Results showed that beam length was negatively associated with behavioural lateralization irrespective of structural measure. A second analysis using a composite score of the four antler measurements, one for each structural measure, showed that only antler symmetry was negatively associated with lateralization during lateral display. Therefore, our second prediction was supported. We discuss these findings in relation to predator detection capability and stress reduction in prey species such as the fallow deer.
Keywords: Aggression; antlers; behavioural lateralization; developmental instability; fluctuating asymmetry.