FOOD AVAILABILITY AND FORAGING BY WILD COLONIES OF DAMARALAND MOLE-RATS (CRYPTOMYS DAMARENSIS) - IMPLICATIONS FOR SOCIALITY

We investigated some of the ecological determinants of sociality in th e Damaraland mole-rat, including the spatial distribution and biomass of resources (geophytes) available to foraging Damaraland mole-rats in partly vegetated sand dunes in the Kalahari and in grasslands near Do rdabis, Namibia, and the foraging behaviour and residency characterist ics of colonies at Dordabis. In both study areas, the geophytes had a clumped distribution, but the highest coefficients of dispersion and m ean biomass occurred in the Kalahari where the principal food was the gemsbok cucumber. However, because the coefficient of digestibility wa s lower in geophytes from the Kalahari than from Dordabis, and the mol e-rats only ate about half of a gemsbok cucumber, there was less energ y available to mole-rats in the Kalahari. At Dordabis, large establish ed colonies occur in the areas with the richest resources and remain r esident in the same area for many years; within this area they search (blindly) for food during brief periods when the soil, al burrow depth , is moist and easily worked. Initially. lone. straight burrows are du g and few bulbs are taken; once the soil dries, minor changes are made to the burrow system as the mole-rats exploit the food patches they l ocated immediately after the rain. Our results show that the character istics of the resources, and the short time interval during which loca tion of new resources is possible, favour group living; however, the c onstraints imposed by these features affect large and small colonies i n different ways. Small colonies are more likely to fail than large on es and some crucial factors in the survival of these newly formed colo nies are the richness of the area in which their burrows are located, and the size of the colony work force available to locate the food.