DIET ALTERS METABOLIC-RATE IN THE YELLOW-BELLIED MARMOT (MARMOTA-FLAVIVENTRIS) DURING HIBERNATION

We investigated the hypothesis that dietary composition can alter metabolic rate in the marmot. We provided marmots with two different diets: Purina standard Rodent Chow (no. 5001) and an essential fatty acid deficient (EFAD) diet (Purina chow no. 5803C). Metabolic rate was determined by indirect calorimetry during the summer and winter season. The mean metabolic rate measured during the summer was 7.54 mL O-2 min(-1) kg(-1) +/- 0.62 for the control group and 7.43 mL O-2 min(-1) kg(-1) +/- 0.34 for the EFAD animals. Both animal groups gained weight during the summer; body weights peaked in September. Fatty acid analysis of white adipose tissue from each group revealed significant differences (P < 0.01) in percent composition of fatty acid species 16:1, 18:1, 18:2, 18:3, and 20:0. Winter mean metabolic rates for the control group were significantly lower (P < 0.05) than they were for EFAD animals for all stages of hibernation (entrance, deep hibernation and arousal). Average total hibernating bout length for the control group was 7.76 d, which is significantly higher (P < 0.05) than the 5.72 d for the EFAD group. These results support the hypothesis that essential fatty acids alter the metabolic rate in marmots and are necessary for normal thermoregulation during hibernation