SNELGROVE, J.M.*; BLOB, R.W.; Clemson Univ.; Clemson Univ.: Antler stiffness in moose: patterns of variation in the material properties of antler bone.

Material properties can vary considerably among bones from different body locations that serve different functions (e.g., skull vs. limbs). However, variation in material properties of a single type of bone has rarely been tested. This study performed three-point bending tests on cortical bone specimens extracted from antlers of 20 individual moose (Alces alces) to test for three types of variation in bone stiffness (Young�s modulus): (1) within the antler structure, (2) between populations of moose, and (3) between moose and other deer species. Though superficial portions of the antler, and the antler beam (base), are subjected to higher bending moments than other parts of the antler, there were no significant differences in stiffness between superficial and deep portions of the beam, or between the beam and the distal brow tine. Moose from Michigan and the Yukon also did not differ significantly in antler stiffness, even though Yukon moose have a shorter growing season and must grow antlers more rapidly. However, moose have significantly stiffer antlers (mean 11.6 � 2.7 GPa) than any other deer in the odocoileine lineage (the clade to which moose belong). The unusual palmate shape of moose antlers likely subjects their antler beams to higher bending moments than found in other odocoileines, a factor that may have contributed to the evolutionary divergence of moose antler stiffness from that of other members of this clade. Though similarities in the mineral composition of bone across species likely limits the overall range of phylogenetic variation in bone material properties (e.g., no species are expected to have bones that behave like cotton or steel), our results demonstrate that evolutionary diversity in bone material properties can be correlated with phylogenetic differences in mechanical or ecological demands.