The effect of deer exclusion on tick abundance in Japan: the verification based on field experiment for controlling deer density

Instalment of deer fences around agricultural fields may, as a side benefit, reduce the risk of tick-borne diseases in humans. We examined tick (Haemaphysalis) density on the ground after two years of exclusion using three separate deer fences. Deer density in an exclosure (EX) had been kept as zero for 14 years, deer density in an enclosure (HD) had been kept constantly stocked for 14 years with around 20 deer km−2, and the second enclosure (OD) had been stocked for 11 years with around 20 deer km−2, after which time the deer were excluded for two years. Tick densities inside the three fences were monitored for two years after two years of deer exclusion from OD. In the first year, tick density in OD was as high as that in HD, and was significantly higher than that in EX. In the second year, however, tick density in OD decreased to a similar level to that in EX. These results suggest that tick density in the environment decreases after three years of exclusion. Our findings support the effectiveness of culling and fencing of deer with the aim of preventing the risk of tick-borne diseases.