Stability of dominance relationships in crayfish depends on social context

Crayfish form social hierarchies through aggressive dyadic interactions. During hierarchy formation, individual crayfish emerge as dominants or subordinates, and continue to express status-specific behaviours once the hierarchy has stabilized. We found that by briefly introducing a single larger crayfish to a pair of juvenile crayfish with established social ranks, the dominance relationship between the initial pair was quickly disrupted and reversals of ranks were common. The intruder crayfish repeatedly defeated both opponents, and, after the intruder was removed, initial subordinates emerged as new dominants and former dominants became new subordinates in half of all pairs. Dominance relationships always remained stable over the entire observation period in control pairs without intruders. Our results show that social status in crayfish is a highly transient and reversible condition. Since agonistic encounters with changing opponents are commonly observed under natural conditions, subordinate crayfish will have numerous recurrent opportunities to gain more preferred social status and dominant crayfish may only hold preferred status for brief periods. Thus, stability of social status depends on social context, and the negative and positive consequences associated with different social ranks may be less permanent than previously assumed.