Spatiotemporal changes in antlerless proportion of culled Sika deer in relation to deer density

Population management of herbivores is widely applied to decrease damage to forests in the northern hemisphere. Culling more antlerless deer, including females and fawns, is an effective means of reducing the population and helps to improve management efficiency. To increase the efficiency of antlerless-biased culling, we assessed the spatiotemporal distribution of the antlerless ratio in culled sika deer (Cervus nippon) in relation to population density. We hypothesized that the antlerless ratio is higher at the center of the distribution than at the margins of the deer's range, because dispersal processes differ according to sex and age: Young male deer first disperse into an unoccupied area, and then males may become established in the new area for approximately 10-15 years before the number of females increases. A statistical model revealed spatiotemporal changes in the antlerless ratio of culled sika deer. The change in the ratio basically fit the density distribution of the deer, which was estimated independently on the basis of fecal pellet count surveys. The antlerless ratio estimated from the model increased asymptotically as deer density rose. The results support our hypothesis and suggest that antlerless sika deer will be more easily culled at the center rather than at the margins of the distribution range. These findings should help to increase the efficiency of managing the deer via antlerless-biased culling.