Fluctuating asymmetry in elk Cervus elaphus antlers is unrelated to environmental conditions in the Greater Yellowstone Ecosystem

摘要

Fluctuating asymmetry (FA) is a measure of the deviation from perfect bilateral symmetry, and has been used across mammals as a reliable indicator of environmental stress during growth and development. Antler size and symmetry can be an indicator of individual fitness and social rank among ungulates such as the North American elk Cervus elaphus. When environmental conditions are favourable, ungulates allocate additional resources to antler development to increase secondary Sexual traits and enhance reproduction. We tested whether there was an appreciable change in antler length and the number of points as extreme climatic conditions (e.g. heavy snow and drought) reduced the nutritional condition of elk using 8,690 antler measurements collected at hunter check stations in south-central Montana surrounding the Greater Yellowstone Ecosystem (GYE) during 1982-2006. We also hypothesized that FA in elk antlers would increase at high elk density because of density-dependent competition for food. We developed a priori general linear models of FA expressed as a function of climate covariates, elk density and relevant ecological interactions between the variables. In contrast to previous studies, especially of European ungulates, our results show little support for strong effects of climate or density oil FA in length or the number of points. Thus, North American elk do not appear to respond to environmental variation by varying allocation to antler growth, instead they show stronger age-related effects oil FA.