Water Intake in Two Coexisting Desert Rodents, Acomys cahirinus and Gerbillus dasyurus

Abstract

The common spiny mouse, Acomys cahirinus ( X body mass = 48 g), and Wagner's gerbil, Gerbillus dasyurus ( X body mass = 33 g), are omnivorous Old World rodents that coexist in rocky habitats in the deserts of Israel. They differ in their diets in that A. cahirinus consumes proportionately more snails and animal matter than G. dasyurus and G. dasyurus consumes proportionately more seeds than A. cahirinus . Rodents were offered seeds and either water ad lib., ca. 50% of ad lib. total water intake, or denied water. Both species were able to maintain steady state body mass on both ad lib. and 50% ad lib. water. Furthermore, both species lost body mass when denied water. However, the daily rate of loss of body mass of G. dasyurus was slower than that of A. cahirinus both in absolute (0.72 and 1.72 g) and in relative (10.9 and 21.9% body mass/g0.54) terms. Dry matter digestibility and metabolizable energy from seeds were similar between species on the ad lib. and 50% ad lib. water treatments and both species combined averaged 90.9% of dry matter and 88.8% of gross energy, respectively—these values were similar to those found for granivorous rodents in general.