Shelter availability influences social behavior and habitat choice in crayfish, Orconectes virilis

Conspecific distribution across differing microhabitats may arise due to individual differences in resource requirements, vulnerability to predation, environmental tolerances, and as a direct result of social interaction. The aim of this study was to examine crayfish distributions across habitats with varying resource availability and to examine whether such distributions are correlated with dominance relationships among individuals. Agonistic interactions, habitat use, and shelter use were observed in mixed-sex populations of eight crayfish, Orconectes virilis. Populations were placed in a semi-natural, 4 x 4 m arena for 20 h that was split into shelter-poor (low), shelter-rich (high) and shelter-free (free) areas. The presence of shelter was associated with a significant increase in crayfish habitat use. Overall agonism also increased in habitats where shelter was present. Status specific differences in shelter and habitat use were observed and were dependent upon environmental context (e.g., day versus night). Lower ranking crayfish were found to occupy and defend shelter less frequently than dominant crayfish and low ranking crayfish were also found more often in shelter-poor habitat. These status-specific differences in behavior were only observed during the day when shelter-related behaviors were increased overall. Distinct shelter use strategies were also apparent between top-ranked (alpha) and bottom-ranked (omega) crayfish. Taken together, these results suggest that shelter use and habitat use are, in part, mediated by social status. Additionally, these results indicate that habitat selection may arise as a consequence of status-specific differences in resource use.