Recognition of Dominance Status By Chemoreception in the Red Swamp Crayfish, Procambarus clarkii

We tested the hypothesis that chemical signals play a role in the recognition of dominance status in the red swamp crayfish, Procambarus clarkii. Dominance was judged on the outcome of dyadic interactions in all male or female groups of three individuals. This resulted in a dominant, intermediate, and subordinate individual within each population. A choice paradigm in a flow-through Y maze was used to judge whether crayfish were able to recognize dominance through chemical cues alone. Both individuals that interacted with the animal producing the odor and naive individuals were tested. Irrespective of sex and previous experience, individuals increased their rates of locomotion in the presence of conspecific odor. Naive males investigated the dominant arm first, spent more time at the dominant nozzle, and responded more aggressively (as measured by meral spread) to dominant male odor and subordinate female odor. Intermediate males spent more time at the dominant male nozzle and responded more aggressively to dominant male odor. Naive females spent more time at the dominant nozzle. These results show that males recognize dominant animals. Since both naive and experienced males respond to water from dominant animals, we concluded that this is recognition of dominance and not just individual recognition. This signal may be important for the formation or reinforcement of dominance relationships. Based on the change in behavior between odors, we suggest that crayfish can use chemical cues to recognize the dominance status of conspecifics.