DICKEY, Brad; University of Kentucky, Lexington; University of California, Davis: Effect of Resource Enrichment on the Social Structures of Crayfish

Social structures affect access to resources such as shelters and food, but changes in the environment affect the dynamics of the social structure and the behaviors of the group members. These reciprocal effects make it difficult to predict how groups and individuals will be affected by environmental changes. To determine the effects of resource abundance on crayfish social structures, I exposed different groups of crayfish to high and low food environments. I found that rank influenced the ability of an animal to possess and consume the food item that was added to the arena, but dominant individuals were not able to monopolize the food items due to an initial period of scramble competition. Groups exposed to high food abundance did not differ significantly from control groups in linearity or tightness of their social structure, but the pattern of interactions among ranks did change: dominants in low resource environments interacted primarily with low status individuals, while in high resource environments dominants interacted mainly with high status individuals. I also found changes in the types and locations of interactions, with many more interactions taking place in shelters when food was added to the environment, and a shift from a linear to a despotic distribution of wins in escalated interactions.