Food availability and foraging by wild colonies of Damaraland mole-rats (Cryptomys damarensis): implications for sociality |
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Authors: | Jennifer U M Jarvis Nigel C Bennett Andrew C Spinks |
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Institution: | (1) Department of Zoology, University of Cape Town, Rondebosch, 7700, Cape Town, South Africa, ZA |
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Abstract: | We investigated some of the ecological determinants of sociality in the 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 Dordabis, Namibia, and the foraging behaviour and residency characteristics of colonies at Dordabis.
In both study areas, the geophytes had a clumped distribution, but the highest coefficients of dispersion and mean biomass
occurred in the Kalahari where the principal food was the gemsbok cucumber. However, because the coefficient of digestibility
was lower in geophytes from the Kalahari than from Dordabis, and the mole-rats only ate about half of a gemsbok cucumber,
there was less energy available to mole-rats in the Kalahari. At Dordabis, large established colonies occur in the areas with
the richest resources and remain resident in the same area for many years; within this area they search (blindly) for food
during brief periods when the soil, at burrow depth, is moist and easily worked. Initially, long straight burrows are dug
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 located immediately after the rain. Our results show that the characteristics of the resources, and the short
time interval during which location of new resources is possible, favour group living; however, the constraints imposed by
these features affect large and small colonies in different ways. Small colonies are more likely to fail than large ones and
some crucial factors in the survival of these newly formed colonies 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.
Received: 6 May 1997 / Accepted: 21 August 1997 |
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Keywords: | Foraging Sociality Bathyergidae Mole-rats |
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