NEUFFER, Jacquelyn, M. *; NAIDITCH, Sarah, E.; HARRIS COTNER, Sehoya, C.; WOODWARD, Denise: Aggression in Fiddler Crabs, Genus Uca: Part 1

Male fiddler crabs (genus Uca) are known for their single, large cheliped. This large claw is believed to be beneficial for a male during courtship and fighting. Several attempts have been made to clarify (a) the role of fighting in fiddler crab interactions, and (b) factors that ultimately determine success in aggressive interactions. This study examined inter- and intra-specific aggression among three species of fiddler crabs–Uca musica, Uca latimanus, and Uca crenulata –in Laguna Juluapan of Santiago Bay (Jalisco, Mexico). Our main focus in this portion of the study was to view the effects of crab size and crab species on fight duration and outcome. Sixteen U. musica, 15 U. crenulata, and 14 U. latimanus were collected, marked, and returned to a densely populated area on the beach. We followed each marked crab, and filmed several male-male encounters between an aggressive wanderer (AW) and a burrow holder (BH). The AWs average between 1.2 and 1.6 fights per excursion. In these fights U. musica wanderers fight all three species, Uca crenulata wanderers fight other U. crenulata and U. latimanus fight U. crenulata. Our preliminary data confirm that the BH is most likely to resume occupancy of its burrow, yet in several instances the AW is able to evict the BH. In our analysis, we focus on the size of the crabs involved versus the duration of each encounter, along with the relationship between the species involved versus the duration of the encounter. Finally, we address instances in which wanderers are able to take over an occupied burrow.