The Atlantic mangrove fiddler, Uca thayeri, is one of approximately 97 species belonging to the family Ocypodidae (Rosenberg 2001). Members of this family are characterized by a thick, squarish body and herding behavior (Ruppert & Fox 1988). Male crabs also bear one greatly enlarged pincer, either right or left (Negreiros-Fransozo et al. 2003), for combat and mating rituals; whereas, the claws of females are roughly equal in size. Fiddler crabs share many common morphological characteristics and behaviors, but identification of species is usually easily achieved through examination of body color and claw structure. The carapace and major claw of U. thayeri are both brown to orange-brown (Crane 1975, Kaplan 1988), and both fingers of the claw are bent down (Ruppert & Fox 1988).