Factors Determining Leg Length in Rangifer tarandus

Abstract

Leg length is quite variable within both domestic reindeer (Rangifer tarandus ssp.) and among the wild subspecies of R. tarandus, and appears to be under the control of several selective factors. These include nutritional constraints, the energetic efficiency of foraging through snow of various depths, the efficiency of locomotion where long migrations occur, and fleetness related to predator avoidance. The net energy cost of walking or running a given distance on a hard surface decreases with increasing leg length, and the advantage of increased leg length in decreasing the cost of locomotion is even more pronounced in deep snow. However, the energetic advantages of long legs for movement in deep snow and for migration are counteracted by the energy costs to the animal for growth and maintenance of the additional tissues and possible decreased efficiency in foraging at or near ground level. The cline of decreasing leg length in Rangifer with increasing latitude is apparently the product of these selectiv...