Maximum Metabolic Rate of Rodents: Physiological and Ecological Consequences on Distributional Limits

Abstract

In this work we determine the maximum metabolic effort of rodents under extreme thermal conditions. We expected that species living under cold conditions would show higher maximum metabolic capabilities than species inhabiting tropical and intermediate habitats. Maximum weight-specific metabolic rate for temperature regulation (MMR) of rodents decreases allometrically with body size (W) but with a different slope than that for basal rate (-0 338 vs -0 25). Deviations from the MMR/W curve are apparently associated with the thermal climate of the species. Analogous species from climatically extreme environments present maximum (body-ambient) thermal differentials (ATM) and weight-specific values that depart from the A TM/Wcurve. Convergence of both MMR and ATM values was found among species with similar climatic/geographic ranges. Maximum energetic capabilities and geographic distribution appear to be correlated. Key-words: Maximum metabolic rate, rodents, thermal climate, lower lethal temperature, distributional limits