Energy Expenditures by Caribou while Cratering in Snow

Abstract

The rate of energy expenditure by caribou (Rangifer tarandus granti) digging in snow for lichens was determined by heart rate telemetry and an analysis of cratering mechanics. Based on a significant linear relationship between energy expenditure and heart rate, the mean cost per digging stroke in light, uncrusted snow was 118 J, whereas in denser (0.36 g/cm3) snow with a thin, hard crust the mean cost was 219 J/stroke. The cost of cratering through snow compacted by a snowmobile was 481 J/stroke. A comparison of metabolic and mechanical energy required for cratering suggested that caribou have evolved an energetically-efficient mechanism for obtaining food from beneath the snow layer.