ECOLOGY OF TROPICAL HERMIT-CRABS AT QUIRIMBA ISLAND, MOZAMBIQUE - A NOVEL AND LOCALLY IMPORTANT FOOD SOURCE

The semi-terrestrial hermit crabs Coenobita cavipes and Coenobita rugo sus are both highly abundant in the supra-littoral zone of Quirimba Is land, northern Mozambique. In the open sand scrub environment the prin cipal food sources were mangrove propagules and algae for C. cavipes a nd rotting terrestrial vegetation for C. rugosus. Increased use of the mangrove habitats on Quirimba Island by the local human population ha s resulted in human faeces as a potential source of food for hermit cr abs. The level of use of this resource differs between the 2 species a nd between habitats, but not significantly between day and night. Both species exhibited gregarious behaviour on food items, particularly C. cavipes on human faeces (up to 61 individuals on 1 food item). Both s pecies exhibited cannibalism during the study period, but this constit uted less than 1% of their diet. The foraging distances of both specie s increased with individual size and differed with habitat in C. cavip es.