Seasonal energy expenditures and thermoregulatory responses of moose

Abstract

Metabolic rates and thermoregulatory responses were studied in adult moose (Alces alces) exposed to various ambient temperatures during winter and summer. Resting energy expenditures followed a marked annual cycle with a maximum (940 kJ kg body weight −0.75 d −1 ) during spring – early summer and minimum (430 kJ kg body weight −0.75 d −1 ) during winter. The heat increment of feeding associated with a pelleted ration was 6–9 kJ kg body weight −0.75 h −1 . The energy cost of standing was 4.2 kJ kg body weight −0.75 h −1 , an increment of 25% over the lying posture. Although piloerection was observed between −25 and −30 °C, metabolic rates did not increase. In contrast to their cold tolerance, moose were easily heat stressed. During winter, moose increased respiration rates when ambient temperatures rose above −5 °C. Resistance to heat load was greater for standing moose during summer; respiration rate increased above 14 °C and open-mouthed panting began at 20 °C. Energy expenditure and heart rate followed a similar rise with increasing ambient temperature.