An Energy Model for Adult Female Caribou of the Denali Herd, Alaska

Abstract

Estimates of the energy costs of resting, activity, and productive processes from the literature were applied to caribou activity budgets and movements documented during 1978-80 to estimate seasonal and annual energy requirements of adult female caribou (Rangifer tarandus granti) in Denali National Park and Preserve. Energy requirements were 45% lower in winter than summer, primarily because of a 21% reduction in resting metabolic rate and benefits of fat catabolism in winter, and high summer costs of lactation, fat deposition, and activity. Estimated energy requirements totaled 38.2 MJ day-1 during the insect season, 36.7 during summer migration, 34.2 during fall migration, 31.9 during prerut and rut, 29.3 during calving and postcalving, 23.7 during early and late winter migrations, 21.6 during early winter, 20.9 during late winter, and 20.5 during midwinter. Annual energy requirements, including costs of pregnancy (368.6 MJ) and lactation (560.3), totaled 9,870 MJ, excluding costs of cratering through snow and apparently minor costs of physiological stress. Compared to studies of food energy requirements of penned caribou, the model gives accurate predictions of total metabolizable energy requirements when allowances are made for the relative inactivity of penned animals.