A novel method of assessing dominance hierarchies shows nuance, linearity and stability in the dinosaur ant Dinoponera quadriceps

Many social species with relatively simple societies have dominancehierarchies of individuals, with dominant individuals achieving fitnessand subordinate individuals either queuing to obtain fitness or achievingonly indirect fitness by helping relatives. Assessing the dominance hierar-chy in a social group is generally based upon observing dyadic interactionsas and when they occur spontaneously within the whole-group setting.However, this method can be very time-consuming because many dyadsinteract only very rarely, necessitating either extremely long observationperiods or many dyadic relationships being unresolved. Here, we reportan alternative method using the queenless dinosaur ant Dinoponera quadri-ceps, which lives in colonies containing tens of individuals. We removedall individuals from their nest and observed the dominance behavioursexpressed in isolated dyadic interactions for every pairwise combinationof individuals. Individuals showed a classic dominance behaviour in thissetting, and the rapid nature of the assay allowed us to observe every dya-dic relationship on a weekly basis over 4 weeks. The dominance hierar-chies based on these isolated dyadic interactions correlated well withthose produced by the conventional method of colony observations. Theyshowed the hierarchies to be highly linear and stable, and also revealedthat dominance relationships may extend further down the hierarchythan previously thought. Although highly manipulative, the isolated dya-dic interaction method works well and will likely make more feasible thestudy of other social species in which pairs of individuals can be isolatedtogether.