It pays to be fickle: dominance and behavioural types in a queenless ponerine ant
Lorenzo Roberto Sgobaro Zanette, Lorenzo Roberto Sgobaro Zanette
Departamento de Biologia, Universidade Federal do Ceará, Fortaleza, Brazil; Departamento de Biologia, Universidade Federal do Ceará, Fortaleza, Brazil
Hierarchies are a fundamental feature of most group living organisms. Reflecting asymmetries between group members, they define how resources and reproduction are shared within the group. In small insect societies, lacking morphological caste specialization, behaviour is a major source of within group variation. We investigate how consistent are individual behavioural differences within colonies of the queenless ponerine ant Dinoponera quadriceps and whether consistency has an effect on the establishment of dominance hierarchies. In total, 228 ants from 22 colonies were used to characterize consistency in activity patterns, aggressiveness and risk-taking behaviours. In the first set (156 ants, 13 colonies), independent of rank, individuals showed consistent activity patterns (Repeatability = 0.22 - 0.48; P = 0.02 – 0.001) and aggressiveness toward conspecifics and a simulated attacker (Repeatability = 0.48 - 0.54; P = 0.001). Dominant ants (top 5 ranks), however, were highly inconsistent in their risk-taking behaviours (Repeatability = 0; P = 0.86), as oppose to low rank foragers that were highly consistent (Repeatability = 0.76; P = 0.001). In the second set of experiments, 72 low rank foragers were isolated in 12 groups. In the newly formed hierarchies, independent of rank, ants were inconsistent in their risk-taking behaviours (Repeatability = 0 - 0.19; P = 0.924 - 0.203). As in the initial natural colonies, aggressiveness was consistent for all ranks (Repeatability = 0.32 - 0.47; P = 0.001), but activity patterns were only consistent for the new dominants (Repeatability = 0.32; P = 0.001). Our results indicate that individual differences in aggressiveness, although consistent, do not affect hierarchy formation. In contrast, activity patterns and risk-taking behaviours are context/rank dependent. Interestingly, high rank individuals may need to be flexible risk-takers while maintaining consistent levels of activity.