Physiological Correlates of Demographic Patterns in Three Sympatric Namib Desert Rodents

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Abstract
Water metabolism in three sympatric Namib Desert rodents (Gerbillurus paeba, Desmodillus auricularis, and Rhabdomys pumilio) was measured using a complete water-balance methodology, with the objective of relating physiological characteristics to population-level properties in these species. Desmodillus auricularis was found to be capable of maintaining water balance on a diet of considerably lower water content than that needed by the other two species. Physiological differences among these species are correlated with differences in (a) their reproductive response to the provision of drinking water in an earlier field experiment; (b) the seasonality of their demographic patterns; and (c) particular features of their life histories. An argument is presented that the water-conserving abilities of these species are intimately related to population processes: G. paeba and R. pumilio, with relatively high water needs, are restricted to breeding during brief periods of high water availability, and their lifehistory traits reflect that high degree of seasonality; conversely, the lower free water needs of D. auricularis permit a relatively aseasonal demographic pattern, and its life-history attributes differ accordingly from those of G. paeba and R. pumilio.