title: Field metabolic rates and water influxes of two sympatric Gerbillidae:Gerbillus allenbyi andG. pyramidum.
abstract: Two primarily granivorous rodents of Old World deserts,Gerbillus allenbyi (mean adult body mass=26 g) andG. pyramidum (mean adult body mass=40 g), coexist in sandy habitats in the northwestern Negev desert. Both species are burrow dwellers and are nocturnal; however, in their overall distributions,G. pyramidum occurs in more extreme deserts than doesG. allenbyi. In comparing field metabolic rate (FMR) and water influx of the twoGerbillus species, we considered two alternative hypotheses: (1) given the difference in their overall distributions,G. pyramidum has a lower FMR and water influx thanG. allenbyi, and (2) given the similarity in their diets, and that we worked with sympatric populations, FMR and water influx are similar. The latter alternative proved to be correct. Field metabolic rates in summer were 7.29 kJ · g-0.51· day-1forG. allenbyi and 7.74 kJ · g-0.51· day-1forG. pyramidum, values that were 69.3% and 74.5%, respectively, of those predicted for rodents of their body masses. Summer water influx ofG. allenbyi was 0.167 ml · g-0.90· day-1and that ofG. pyramidum was 0.144 ml · g-0.90· day-1; these values were 79.4% and 68.6%, respectively, of water influxes predicted for rodents of their body masses. When compared allometrically, there were no interspecific differences in any of the measurements.
authors.affiliation: Isan Center for Comparative Medicine and Desert Animal Research, Jacob Blaustein Institute for Desert Research, Ben-Gurion, University of the Negev, 84105, Beer Sheva, Israel.
authors.forename: A Allan
authors.initials: AA
authors.lastname: Degen
authors.affiliation: Mitrani Center for Desert Ecology, Jacob Blaustein Institute for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, 84993, Israel.|Department of Life Sciences, Ben-Gurion University of the Negev, Sede Boqer Campus, 84993, Israel.
authors.forename: Berry
authors.initials: B
authors.lastname: Pinshow
authors.affiliation: Isan Center for Comparative Medicine and Desert Animal Research, Jacob Blaustein Institute for Desert Research, Ben-Gurion, University of the Negev, 84105, Beer Sheva, Israel.
authors.forename: Michael
authors.initials: M
authors.lastname: Kam
keywords: Field metabolic rate; Gerbillus allenbyi; Gerbillus pyramidum; Granivorous desert rodents; Water influx