Energetics of hibernating yellow-bellied marmots (Marmota flaviventris)

Yellow-bellied marmots (Rodentia: Sciuridae) typically hibernate for eight months. This study explored energetic costs of hibernation in young and adults at 10 and 6 degreesC. Age significantly affected the percent time torpid, total and mass-specific VO2, use of energy during torpor, and daily mass loss at 6 T. Thus young had a higher mass-specific VO2 during a torpor bout, which was attributed to higher metabolism during deep torpor. Total VO2 during a bout was higher in young and there were significant temperature/age interactions; young had a higher VO2 during torpor and deep torpor at 6 degreesC than at 10 degreesC. VO2 increased at T(E)s below 6 degreesC. Young had a higher daily mass loss than adults at 6 T. Euthermy increased energetic costs 19.3 times over those of torpor and 23.5 times over those of deep torpor. Energy costs are minimized by spending 88.6% of the hibernation period in torpor, by the rapid decline of VO2 from euthermy to torpor and by allowing T-B to decline at low T-E. Torpidity results in average energy savings during winter of 83.3% of the costs of maintaining euthermy. Energy savings are greater than those reported for Marmota marmota and M. monax. (C) 2002 Elsevier Science Inc. All rights reserved.