Agonism does not covary with territoriality in a gregarious reptile

Abstract

Natural selection for territoriality is theorised to occur under conditions favouring intra-sexual phenotypic variation in physiology, morphology, and behaviour. In this context, certain suites of behavioural traits associated with territoriality are expected to consistently covary among individuals (sometimes referred to as ‘behavioural syndromes’) within sexes. Agonism (conflict-associated behaviours that may or may not be associated with physical aggression) and movement—for example, ranging, or relocation within or across seasons—are two behavioural components that are associated with territoriality and may be expected to covary in this context. Territorial males are expected to employ agonistic behaviours to actively establish and defend areas and resources and show more stability in their location across the landscape. However, the interaction between agonism and movement especially for wild reptiles has rarely been tested. We investigated whether agonistic and movement behaviours correlate at the individual level both within one year and across multiple years, in a wild population of Australian eastern water dragons, Intellagama lesueurii. Although both types of behaviours exhibited among-individual repeatability over year and multi-year scales, we found no evidence of an agonistic-movement behavioural syndrome. These findings indicate that agonistic and movement behaviours are likely independent traits, and thus, territoriality may not drive shared selective pressures for both. It is possible that other social behaviours and strategies are in place to maintain social structure in this wild population.Significance statementMales of many animals establish and maintain or defend territories. Territory defence is expected to be associated with behaviours associated with conflict or expressions of dominance, to signal territory boundaries to encroaching individuals, or more aggressive approaches for active defence. We investigated whether such agonistic behaviours correlated with the distances individuals ranged or dispersed within and between years, as an indicator of territoriality. Through thousands of observations of a wild population of Australian eastern water dragons, Intellagama lesueurii, we found that although individuals showed repeatable patterns of both agonistic and movement behaviours, we found no evidence that these were correlated. It appears that territory establishment and defence may therefore not rely on agonistic signals in this species in direct contrast to other taxa, indicating that other systems are in place to maintain social structures.