Predicting energy expenditures for activities of caribou from heart rates

Abstract

Highly significant (P<0.001) linear relationships between oxygen comsumption (VO2) and heart rate (HR) were found for six caribou (Rangifer tarandus grand) at several times during the year. The standard error of the estimate for predicting VO2 from HR was within 10% of the mean VO2 for 9 of 13 caribou/season combinations. Energy expenditures by caribou while feeding on grain at a trough, grazing, browsing and walking within a large enclosure were 12%, 17%), 18% and 46% higher than the cost of standing. HR's recorded during a given activity decreased sharply during September and October, and reached a minimum in January. An abrupt increase in HR's of female caribou occurred 3 weeks prior to parturition. Heart rate telemetry can be used to determine the relative energy expenditures of free-ranging caribou with reasonable accuracy.