FIELD METABOLIC RATES OF ACOMYS RUSSATUS AND ACOMYS CAHIRINUS, AND A COMPARISON WITH OTHER RODENTS

ABSTRACT

Golden spiny mice (Acomys russatus) and common spiny mice (Acomys cahirinus) are omnivorous rodents that are sympatric in many rocky areas in Israeli deserts. They are similar in body size and dietary habits, but differ in their temporal activities and overall distributions. A. cahirinus are nocturnal whereas A. russatus are diurnal, and A. russatus inhabit extremely arid areas where A. cahirinus are often absent. Field metabolic rate (FMR) was 1.35 kJ·g⁻¹d⁻¹ for A. cahirinus (mean body mass = 38.3 g) and 1.06 kJ·g⁻¹d⁻¹ for A. russatus (mean body mass = 45.0 g); that is, mass-specific FMR was approximately 27% higher in A. cahirinus than in A. russatus. The linear regression of log FMR (kJ· d⁻¹) on log body mass (m_a; g) for 21 rodent species took the form: log FMR = 0.654 log m_b+log 5.632. A. cahirinus and A. russatus had FMRs that were 85% and 70%, respectively, of those predicted for rodents of their body masses according to the predictive equation. Indeed, the FMR of A. russatus was one of the lowest relative FMRs of rodents in general. When compared allometrically, FMRs of desert rodents were lower than those of nondesert rodents. In addition, granivorous rodents tended to have the lowest FMRs, and herbivorous rodents the highest.