Dominance hierarchies and status recognition in the threatened crayfish, Austropotamobius italicus.

This study aims at investigating the formation and maintenance of dominance hierarchies in the white-clawed crayfish, Austropotamobius italicus, a threatened species in Italy. To this end, we investigated the behaviour of size-matched pairs of intact males and followed an experimental design composed of three phases: (1) isolation for a week, (2) combat for five days, and (3) experimental phase in Day 6. This latter phase consisted in switching individuals of the same or of a different status between 10 pairs and in subjecting the remaining 10 pairs to a sham switch. Therefore, we formed pairs composed of unfamiliar (and familiar) opponents having different (and the same) status. The results show that (a) A. italicus establishes stable dominance hierarchies; (b) A. italicus is able to recognise the status, but not the identity, of its rival; and (c) status recognition is associated with “winner and loser” effects.