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 ce rvid ecology, we measured the stiffness (in bending) of antler from white-t ailed deer (Odocoileus virginianus) and compared our results to previous me asurements from antlers of other cervid species. Stiffness of antler specim ens did not correlate significantly with mineral content or the location wi thin 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, smalle r bucks to have a more effective lever through which their smaller muscular forces can be transmitted during sparring with older, larger bucks. The st iffnesses we measured for white-tailed deer antler are similar to values me asured previously from other members of the odocoileine lineage, which are lower than those previously measured from the antlers of deer living in tro pical habitats. However, confidence limits for maximum likelihood reconstru ctions of the ancestral stiffness of deer antler span the range of high sti ffnesses found among tropical deer; furthermore, parsimony-based reconstruc tions of ancestral antler stiffness are equivocal. Thus, the high antler st iffnesses of tropical deer may reflect the retention of an ancestral condit ion, rather than adaptation to year-round antler use. (C) 2001 The Linnean Society of London.