Fluctuating Asymmetry of White-Tailed Deer Antlers

Abstract

Fluctuating asymmetry has been proposed as an indirect indicator of individual quality. Sexually selected traits, such as deer antlers, are expected to exhibit patterns of decreasing level of fluctuating asymmetry with increasing trait size and decreasing level of fluctuating asymmetry with increasing age. These hypotheses have previously been tested for antlers using linear measures to determine level of asymmetry. However, antlers are complex, 3-dimensional traits making it difficult to quantify all forms of visual asymmetry using linear measures. It is this visual asymmetry that is assessed by potential mates and rivals. Therefore, I created computer models of white-tailed deer (Odocoileus virginianus) antlers to measure visual asymmetry, which may have previously been unaccounted for with linear measures. Asymmetry measures of various antler traits were computed from the models by measuring distances from the trait to a vertical and horizontal plane created within the model. There was no association found between degree of fluctuating asymmetry and trait size, nor was any association found between degree of fluctuating asymmetry and age using either the 3-dimensional measures of asymmetry or traditional, linear measures of asymmetry. These data suggest that fluctuating asymmetry of white-tailed deer antlers is not a reliable indicator of quality. This method used to measure fluctuating asymmetry in antlers could be expanded for use in measuring asymmetry in many complex 3-dimensional traits. Important landmark points were marked on the features of interest, and then digital photographs were taken of each antler set. These landmark points were labeled and cross-referenced across all the photographs, using the program PhotoModeler, to create 3-dimensional “stick” figures. Distances were taken from the important features to a vertical and horizontal plane that was created using the coordinate points generated by the model. By modeling ten sets of antlers twice using the same photographs, the models were found to be highly repeatable.