Seasonal changes in metabolic capacity and norepinephrine thermogenesis in the alaskan red-backed vole: Environmental cues and annual differences

Abstract

1. 1. Wild red-backed voles ( Clethrionomys rutilus) were tested for maximum metabolic rate ( M max) and for metabolic response to norepinephrine ( M NE ) in September, November and January. During the same period, voles born and raised in the laboratory were acclimated (for 3.5 months) in the following groups: (1) +20 C and 24 hr light daily (LD 24:0): (2) +20 C and LD 4:20: (3) gradual change from + 5 C and LD 14:10 to −5 C and LD 4:20; (4) gradual change from +5 C to −5 C and continuous LD 4:20, and tested for M max. 2. 2. During acclimatization of wild voles from September to January M max increased 42% to 23.05 ± 1.19ml O 2·g −1 · hr −1 and M NE increased 59% to 14.12 ± 0.86 ml O 2·g −1·hr −1. Peak winter M max and M NE in these wild voles were lower than found in a previous winter. 3. 3. In voles acclimated to +20 C and either long or short daily light period M max remained unchanged. In voles acclimated to increasing cold and decreasing or short light period M max increased 39% to 20.0 ml O 2·g −1·hr −1. 4. 4. The results indicate that the magnitude of seasonal change of M max and M NE may vary from year to year and suggest that cold is essential to stimulate these seasonal changes in red-backed voles.