Changes in the Deer Population Density Associated with Cattle Grazing

In this study, we investigated the changes in the deer population density associated with cattle grazing. The study was conducted in a woodland pasture-dominated larch (approximately 1,300 m above sea level). The woodland pasture (8.5 ha) used for grazing was surrounded by a barbed wire fence, and four Japanese black cows were grazed there for 1 month from 24 September. Two line transects (3 x 150 m) were set up: one along the fence on the north side of the pastureland and one 150 m away from the fence on the north side as a control area. The vegetation survey and faecal pellet sampling were conducted from 18 September to 6 November 6, 2003, and the amount of grass inside and outside the woodland pasture and the number of faecal pellets in each transect were recorded every week. We randomly selected five harvesting locations for each survey, both inside and outside the woodland pasture, near each line transect. We harvested plants within a 1 × 1 m quadrant frame, and determined the fresh weight of the plants. The deer density was then estimated based on the number of faecal pellets found in each transect. To avoid duplicating records in the following week’s survey, we collected the faecal pellets each time they were found. The amount of grass inside the woodland pasture gradually decreased with the start of grazing. The deer density in both line transects significantly differed during the grazing period (p < 0.01). Immediately after the start of grazing, the density decreased greatly in the transects along the fences. Subsequently, the density decreased with the decrease in the amount of grass. In the control area, the density did not change substantially until the third week of grazing, but decreased in the fourth week. Two weeks after the end of grazing, the density increased in both the line transects. We conclude that the deer may have avoided the area due to cattle grazing.