METABOLIC-RATE AND EVAPORATIVE WATER-LOSS AT DIFFERENT AMBIENT-TEMPERATURES IN 2 SPECIES OF FOX - THE RED FOX (VULPES-VULPES) AND THE ARCTIC FOX (ALOPEX-LAGOPUS)

1. Resting metabolic rate (RMR) and evaporative water loss (EWL) of adult red and arctic foxes were determined over ambient temperature (T(a)) ranges of -13-37-degrees-C and -5-30-degrees-C as oxygen consumption and amount of water in expired air using an open flow system. 2. The average RMR was 2.60 +/- 0.14 W/kg for the winter red fox, 2.59 +/- 0.14 W/kg for the summer red fox, and 2.35 +/- 0.11 W/kg for the winter arctic fox. 3. The rate of increase of RMR was significant (P < 0.05) only for T(a) range above 27-degrees-C. The slopes for this T(a) range were 0.152 for the winter red fox, and 0.283 for the winter arctic fox. 4. The upper critical temperature (T(uc)) of the red fox is probably between 30 and 32-degrees-C. The T(uc)) of the arctic fox is probably between 26 and 28-degrees-C. The lower critical temperatures (T(lc)) were not reached. 5. A strong linear relationship between the EWL and T(a)) was found for T(a) range above 27-degree-C. The slopes for this T(a) range were 0.523 for the winter red fox, and 1.025 for the winter arctic fox. 6. Probably, there are neither significant intraspecific seasonal nor interspecific differences in the RMR and EWL. The two species seem to differ only in their critical temperatures.