Intersexual differences in European lobster (Homarus gammarus): recognition mechanisms and agonistic behaviours

Abstract

Dominance can be maintained through status recognition or recognition of individual (familiar) opponents. In crustaceans, both types of recognition exist, often based on chemical signals. Fight behaviours involved in establishment and maintenance of dominance relationships in male and female European lobster (Homarus gammarus) were examined. Same-sex pairs of size-matched animals interacted on two consecutive days, encountering either the same (familiar) or another (unfamiliar) opponent of the opposite dominance status in the second fight. Results show that both female and male H. gammarus establish dominance in a first encounter, and maintain dominance in a second interaction against a familiar animal, resulting in decreased fight duration and lower aggression levels. Female losers that met an unfamiliar dominant also had short second days with low aggression, while male losers responded to unfamiliar animals with high aggression and long fights. Thus, males distinguish between familiar and unfamiliar opponents, indicating individual recognition whereas females do not, indicating that they use dominance status recognition rather than individual recognition. Female-female fights involved more high-level aggression (claw lock) than male-male fights, contrary to the belief that male lobsters are more aggressive than females. H. gammarus fights also escalated to unrestrained violence fast, indicating low levels of ritualisation. (Less)