Construction and Use of a Direct Calorimeter to Estimate Energy Expenditure in Hibernators

Metabolic rates have traditionally been estimated through indirect calorimetry (gas exchange or respirometry) due to its ease and availability. Oxygen consumption neglects the contributions of anaerobic metabolism, while direct calorimetry (heat production) estimates both anaerobic and aerobic metabolism. Walsberg and Hoffman (2005) report anaerobic metabolism may be more important to small rodents than was previously thought. During the non‐steady state of mammalian hibernation, we hypothesize that anaerobic processes may play an even greater role in fueling metabolism. To address this question, we constructed a very sensitive calorimeter that utilizes the Seebeck effect from a thermoelectric element (Peltier device). We describe its construction, characterization and will use the device to estimate heat production in hibernators this winter. We will compare estimates of energy use from the direct calorimeter from simultaneously obtained respirometry data to provide the most complete picture of energy use during hibernation to date.