The distribution and coexistence of

The distribution and coexistence of the fiddler crabs U. vocans borealis and U. lactea lactea was investigated in
the upper shore of a sandy beach with respect to particle size, water content and total organic carbon content
of the sediments. A clear segregation of habitats between the two species was apparent. U. lactea lactea were
only found in sediments with significantly lower total organic carbon content. U. lactea lactea had a higher
ratio for the size of third maxilliped to body size than U. vocans borealis. There was no statistical difference
in the median sediment particle size of the habitats where both species were found on the study shore. U. lactea
lactea was larger on shores where U. vocans borealis were absent. Smaller U. vocans borealis individuals
occupied sediments with higher water content and finer particles. Smaller individuals of U. vocans borealis
also possessed fewer spoon-tipped setae on second maxilliped than their larger conspecifics, which were
found mostly on coarser sediments. U. lactea lactea spent significantly more time on the surface than in the
burrow during low tide when compared with U. vocans borealis. Both Uca species exhibited similar desiccation
resistance. U. lactea lactea tends to keep its frontal region in close contact with sediments to maintain
moisture when being exposed to air