Recently, sika deer (Cervus nippon yesoensis) populations have caused significant crop losses (about five billion yen in 2009) in Hokkaido, Japan. The losses have been a severe social problem in eastern Hokkaido, which is overcrowded with the deer. We verified the effectiveness of culling and fencing in reducing crop damage over a 16-year period (1994–2009) in eastern Hokkaido. We constructed models that accounted for the crop damage costs associated with the amount of deer harvest and proportion of fence-protected fields on a municipality scale. The models revealed that fencing is an effective countermeasure for preventing crop damage, while culling is not adequately strong to reduce it. Furthermore, agricultural products were protected effectively if the fences covered at least 25% of the boundary between agricultural fields and forest edges. However, the effectiveness of fences declined over time. Our results suggest that increased culling pressure and regular fence maintenance are both required to ameliorate crop losses due to sika deer.
