Look good to die or look poor to survive: antler properties in a malnourished sika deer population

The antlers of male deer function as visual displays of power, and as physical weapons to stag opponents, thereby functioning as determinants of social rank. Thus, stags with long and “magnificent” antlers would have more chances for reproductive success. Cervid antlers are shed every year and are costly. Therefore, stags living in resource-poor habitats face a conflict to invest materials into antlers or to maintain good condition. We compared the antlers of sika deer ( Cervus nippon ) living on a small, over-populated island with limited food resources (“Island deer”) and those of a well-nourished populations on the mainland (“Mainland deer”). The antlers of the Island deer were narrower than those of the Mainland deer, and weight per unit length was lighter. The cortex bone was thinner and the density was lower. The cross section was more biased along the anteroposterior axis presumably to provide mechanical strength to cope with stresses imposed when stags lock antlers and push against one another. Numbers of tines were not different between the populations. The Island stags invested limited resources to antlers to maintain its function through maintaining length by increasing porosity, and maintaining numbers and weights of tines.