Territorial battles between fiddler crab species

Abstract

Many species worldwide are impacted by habitat loss. This may result in increased competition both within species and between species. Many studies have demonstrated that when two previously non-overlapping species are forced to compete over a resource, one species is likely to become dominant over the other. This study explores the impact a larger species of fiddler crab (Tabuca elegans—previously known as Uca elegans) has when invading an area previously used solely by a smaller species (Austruca mjoebergi—previously known as Uca mjoebergi). Here we show that, while there are some detrimental effects of living next to a heterospecific, they are relatively minor. New heterospecific neighbours fight more regularly with resident crabs, but each fight is no longer or more escalated than those between the resident and a new conspecific male. The residents are not specifically targeted by intruding heterospecifics, thus, given the large advantage of having a heterospecific neighbour in terms of lowered competition for females, the overall impact of species mixing is probably not as negative as might have been predicted.