Does Positional Behavior in Fiddler Crabs Depend on Sex or Familiarity?

Animals often position themselves in the environment relative to members of their own species. In the present study, we examined whether fiddler crabs (Uta sp.) exhibit different patterns of burrow use when they are paired with a member of the same sex and whether they have prior experience with the individual they are paired with. Crabs were introduced into test arenas containing two existing burrows on opposite corners of the container. Individuals were monitored throughout the day and positional behavior/burrow preference noted at specific intervals. Experimental pairings included: male-male, female-female, and male-female combinations. Also, some trials were conducted using individuals that had been housed together for prolonged periods prior to the experiment, and other trials with individuals that had never encountered one another prior to the treatment. The results of this study provide a better understanding of the role that acquaintance plays in the gregarious behavior of this species.