Deterrent Effect of Rosin and Wood Tar against Barking by the Gray-sided Vole (Clethrionomys rufocanus bedfordiae)

Abstract

The gray-sided vole (Clethrionomys rufocanus bedfordiae Thomas) is a small wild rodent widely distributed in Hokkaido, northern Japan. Floors of forestry plantations with thick herbage provide gray-sided voles with suitable habitats. The voles eat bark in winter, and because of this, severe damage can occur in many plantations. Deterrent effects on gray-sided voles of rosin and 3 wood tars were evaluated by two-choice tests in the field. These materials were selected because they were promising and economical deterrents. In the test for each material, disks were produced from trunks of Japanese larch, and used as carriers. Pairs of carriers (a material-treated carrier and a control carrier) were fed to gray-sided voles for 24 h, and values of the eaten area of bark were compared between treated carriers and controls. Every material decreased the extent of barking. The treated carriers were significantly less eaten compared to the controls for all the materials (p<0.01 or 0.05). Deterrent effects of three fractions (neutral, phenol, and strong acid fractions) made from wood tar were also evaluated. Every fraction prevented gray-sided voles from barking. The treated carriers were significantly less eaten compared to the controls for all the fractions (p<0.05). The neutral fraction has showed an especially strong deterrent effect; thus this fraction is most promising for future use.