however, have
been directed towards the semi-tropical uciids. In sub-tropical Hong Kong (22200 N;
114100 E), the fiddler crabs U. vocans borealis (Crane 1975) and U. lactea lactea (de
Haan 1935) are widely distributed on sandy shores (Bones, 1983). On many shores,
both species coexist in the upper intertidal zone and share similar home ranges. It is
therefore of interest to explore the factors controlling their distribution in the same
habitat. In the present study, we investigated the distribution of U. vocans borealis
and U. lactea lactea on an intertidal shore and examined whether behavioural adaptations
by these two sympatric species were important for their coexistence on the shore.