DAILY ENERGY-REQUIREMENTS OF BEAVER (CASTOR-CANADENSIS) IN A SIMULATED WINTER MICROHABITAT

Daily energy expenditure, food consumption, and aquatic activity were investigated in beavers housed in a microhabitat designed to simulate winter field conditions. Beavers consumed an average of 0.52 kg/day of woody forage, representing an estimated gross energy intake of 6547 kJ/day. Animals exhibited a distinct daily rhythm in metabolic rate, which averaged 2.87 W/kg, or 1.7 times the basal rate previously reported for beaver. Beavers spent an average of 140.5 min, or about 10%, of each 24-h measurement period in water. Mean daily energy expenditure was 3880 kJ/day, and was independent of both the cumulative immersion time and the frequency of aquatic excursions per day (P > 0.05). Based on previous estimates of the energy content and digestibility of forage cached prior to freeze-up, it is unlikely that the winter energy requirements of this species can be met solely from the submerged food cache.