Feeding and burrowing ecology of two East African mangrove crabs.

The behavior and ecology of two mangrove crabs, Sesarma meinerti De Man, 1887 and Cardisoma carnifex (Herbst, 1794) were investigated at the beginning of the rainy season (October-November 1988) at Mida Creek, Kenya. Both species occupy upper intertidal levels, above mean high-water neap, and completely overlap in their zonation. Each burrow lasts ca. 3 wk, with no significant difference between the species. Both are more active around dusk and dawn and also follow a similar trend in their foraging activity, but differ in that burrowing is mainly diurnal in C. carnifex and nocturnal in S. meinerti. A hierarchy of food preference, established by offering C. carnifex and S. meinerti leaves of five mangrove species, proved similar for both, with Bruguiera gymnorhiza ranking first and Avicennia marina last, but significant only for C. carnifex. A rough estimate of the amount of litter consumed by these two species and of the soil mixed up by their burrowing activity indicates that they play a role of primary importance in the ecology of East African mangroves.