46. The Relative Size of Antlers in Deer

S ummary .1 Data have been obtained, for 527 wild adult specimens, on body‐weight and antler‐weight. These indicate that relative antler‐weight increases with absolute body‐weight, with (except at extremely high body‐weights) a constant partition‐coefficient for antler‐weight of about 1.6. 2 When different regions are considered separately, the mean regional relative antler‐weight also increases with the mean regional absolute body‐weight. 3 Within single regions, however, this trend of relative antler‐weight with increasing body‐weight may be irregular or reversed. Possible reasons for this are discussed. 4 A discussion of the results of the importation of Red Deer into New Zealand confirms the idea that relative antler‐size is primarily a function of absolute body‐size, and not a diagnostic genetic character; it also shows the extreme plasticity of adult body‐weight. 5 The growth of the Red Deer by age is given from the records of Warnham Park (body‐weight, 212 specimens; antler‐weight from a previous paper). The highest age is 14 years. Regression in body‐ and antler‐weight begins to set in at about ten years, and appears to be progressive after this. 6 When antler‐weight is plotted against body‐weight by years, it is found that the partition‐coefficient for ant‐ler‐weight is much higher than within an adult population. It begins at over 3.0, and gradually slows down with age. 7 Data are presented relative to the growth of different parts of Red Deer antlers in successive years. (B) Roe Deer ( Capreolus caprea ). 8 Data for 405 wild adult specimens have been analysed. In this species relative antler‐weight decreases with increasing body‐weight (growth‐partition coefficient about 0.57 per cent. The relative antler‐weight at 16.6 kg. body‐weight is 1.36 per cent., at 28.3 kg. body‐weight is 1.08 per cent. If y=antler‐weight and x = clean body‐weight, in kilograms, the formulae for the two species are as follows:—Red Deer, y =0.00162 x 1.6; Roe Deer, y =0.0455 x 0.57. 9 The range of variation of the Red Deer is much greater than that of the Roe Deer in the character studied. The different is greatest for antler‐weight, intermediate for point‐number, least for body‐weight. 10 Antler‐growth probably reaches its maximum much sooner in Roe Deer, at about four years. 11 When in Roe Deer different regions are considered separately, there is a, slight increase of mean regional relative antler‐weight with increase of mean absolute body‐weight. 12 Within single regions the change of relative antler‐weight with body‐weight is as in Red Deer. 13 Regions which show high relative antler‐weight for Roe Deer tend to show high relative antler‐weight for Red Deer, and the same correlation exists for low relative antler‐weight. 14 The facts here presented make it probable that to diagnose species, and especially subspecies, of deer on size‐characters, whether of total absolute size or relative size of parts, is not taxonomically valid until proof has been given that such characters are genetic and not direct environmental modifications. 15 Data on point‐number in relation to body‐weight are given both for Red and Roe Deer. 16 Some data on Manchurian Deer, Hog Deer, Moose and other species are presented. 17 A suggested interpretation of the opposite results under (1) and (8) is given. It is suggested that in all deer the growth‐partition coefficient for antler‐weight decreases progressively with age; but that, while in Red Deer it normally does not fall below unity before the adult state is attained, in Roe Deer the falling off is much more rapid, and soon falls below unity.