Correlates of variation in deer antler stiffness: age, mineral content, intra-antler location, habitat, and phylogeny

To test correlations between the stiffness of deer antler and aspects of cervid ecology, we measured the stiffness (in bending) of antler from white-tailed deer (Odocoileus virginianus) and compared our results to previous measurements from antlers of other cervid species. Stiffness of antler specimens did not correlate significantly with mineral content or the location within the antler from which specimens were taken in O. virginianus. However, antler stiffness in white-tailed deer decreased significantly between two- and three-year-old bucks, matching the time in O. virginianus life history when males shift from sparring with mostly larger individuals to sparring with mostly smaller individuals. Stiffer antlers may enable younger, smaller bucks to have a more effective lever through which their smaller muscular forces can be transmitted during sparring with older, larger bucks. The stiffnesses we measured for white-tailed deer antler are similar to values measured previously from other members of the odocoileine lineage, which are lower than those previously measured from the antlers of deer living in tropical habitats. However, confidence limits for maximum likelihood reconstructions of the ancestral stiffness of deer antler span the range of high stiffnesses found among tropical deer; furthermore, parsimony-based reconstructions of ancestral antler stiffness are equivocal. Thus, the high antler stiffnesses of tropical deer may reflect the retention of an ancestral condition, rather than adaptation to year-round antler use. (C) 2001 The Linnean Society of London.