Lichen Intake Estimates for Reindeer and Caribou during Winter

Lichen intakes by reindeer and caribou (Rangifer tarandus) during winter were estimated using penned reindeer, esophageal fistulated reindeer, and by the application of the fallout radiocesium method to free-grazing caribou. Estimated mean values for lichen intake as determined by the 3 methods were 16.4, 31.6, and 61.3 g/day of dry lichen per kg body weight or approximately 1.3, 2.5, and 4.9 kg/day dry lichen for an 80-kg reindeer or caribou. The 4-fold range in lichen intake estimates may be attributed to differences in environmental exposures inherent in the methods. Penned reindeer were necessarily sedentary without the stresses and activities normally associated with free-grazing animals. Esophageal fistulated reindeer were required to obtain forage for themselves. However, they were tethered or protected and therefore not subjected to influences such as migration or harassment by predators. The fallout radiocesium method is unique in that it does not affect the normal activity of the animal and thus has the potential for determining the most realistic estimate of lichen intake for an animal in the natural system. The forage intake rates in terms of metabolizable energy available to reindeer and caribou are compared to the probable energy requirements of the animals.