Voles, Microtus spp.

Conifers
Fig. 282   Plantation damage resulting from extensive vole activity.	Fig. 283   Clipping of terminal and lateral shoots of lodgepole pine seedling by voles.	Fig. 284   Sapling completely debarked by voles.	Fig. 285   Surface runway of voles.
Broadleaves
Fig. 419  Vole damage to willow.	Fig. 420   Apple tree girdled by vole.	Fig. 421   Vole droppings.

Distribution:  Throughout B.C. except the Queen Charlotte Islands.

Tree Species Attacked: Conifers - Commonly damaged tree species include Douglas-fir, western hemlock, lodgepole pine, spruce, western redcedar, and grand fir. Voles commonly feed on seedlings and less commonly, saplings.

Broadleaves - Trembling aspen, black cottonwood, hybrid poplar, and sometimes red alder are damaged by voles.

What To Look For:  Fuzzy patches of gnawed bark around the base of the tree, clipping by several cuts, runways, and droppings.

Signs & Symptoms: Voles clip the terminal and lateral shoots of small seedlings, leaving a rough, oblique cut. Larger seedlings and saplings are debarked and often girdled. The bark is gnawed rather than stripped, giving the exposed sapwood a fuzzy appearance. Toothmarks are indistinct, averaging 1.5 mm wide and 8 mm long, and resemble light scratches. Irregular patches of gnawed bark can also be seen on the roots, root collar, lower stem, and occasionally on the lower branches. Girdling can be examined by brushing the duff and soil from around the damaged tree. Small runways can be found in the grass and small piles of clipped vegetation occur along these paths. Small tunnels can occur in soft soil. Vole droppings are cylindrical, have round ends, and are about 5 mm long. Locations where voles are a problem are clearcuts with lush, grassy-brushy vegetation, near a water source.

Damage: Most damage occurs during very high population densities (every 3 to 4 years) over the winter and can be extensive in some plantations. Winter feeding usually takes place under the snow in the interior. Small seedlings have reduced growth or are killed as a result of clipping. Growth rates of larger seedlings and saplings can also be adversely affected by feeding activities on the roots, root collar, lower stem, and lower branches. Girdling of these trees causes scattered mortality. 

Heavy losses can occur in black cottonwood and hybrid poplar plantations. Voles create the largest potential impediment to plantation establishment for native cottonwoods and hybrid poplars. Vole damage can occur on trees 10 to 12 m tall.

Similar Damage: The brown lemming can cause similar damage in the northwest portion of the province. The oblique cutting of shoots is similar to hare damage, but vole cuts are rougher due to the several cuts required to sever the stem. Rabbits or hares make a single, clean, oblique cut to stems and branches and leave teeth marks on gnawed bark.

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Contact Tim Ebata if you have comments on the presentation of this information.

BC Ministry of Forests
Forest Practices Branch
P.O. Box 9513 Stn. Prov. Gov.
Victoria, BC
V8W 9C2

Section phone: (250) 387-8739
Section fax: (250) 387-2136

Last updated March 04, 2002