Variation in mandible length and body weight of Red deer (Cervus elaphus)

The range of intra-specific variation in morphological characters has rarely been examined by taxonomists, and subspecies have often been named on the basis of as few as two skulls. However, despite the limitations set by the material data, taxonomists have long recognized an apparent cline in nose length of Red deer ( Cervus elaphus L.) between the eastern and western extremities of its European distribution. Since larger samples of mandible and body weight data have recently become available for three widely separated populations within the north western parts of their range—the Isle of Rhum (north-west Scotland), Grizedale (north-west England) and Oksbol (Denmark)—it has become possible to examine this cline critically in relation to age, development and geography. In all three populations, the relationship between body weight and jaw length differed significantly at the 1% level, but, as expected, whilst the deer from Denmark had the longest mandibles as adults, as juveniles they had the shortest mandibles in relation to body weight. Furthermore, if the island of Rhum was divided arbitrarily into three areas, namely north western, south western and eastern, an exactly similar picture emerged. Therefore, no single simple law such as Bergman's rule seems to offer an entirely satisfactory explanation.