Sex recognition and agonistic strategies of male and female crayfish

Intraspecific communication is essential for agonistic and mating behaviours. Agonistic strategy of males must change according to the sex of opponents and that of females is also dependent on their physiological state as to whether they are brooding or not. We have analysed here the agonistic encounters between pairs of male and female crayfish in various combinations to reveal the interaction between agonistic and mating behaviours. After male crayfish became dominant, they aggressively chased subordinate males with attacks, while they did not attack female opponents. Furthermore, the agonistic behaviour of males changed depending on whether females were ovigerous or not. On the other hand, two females showed intense combats despite being ovigerous or not. Crayfish discriminated the sex of opponents via chemical signals in the urine. However, the dominant and subordinate social order of crayfish had no effect on selecting mating partners.