Meadow Mouse Girdling--Another Cause of Death of Reseeded Bitterbrush Plants

Abstract

During 1957 and 1958, a population irruption of the meadow mouse (Microtuis tnontanus) occurred in northeastern California and Oregon. The mice moved from their normal habitat into marginal areas, including the sagebrush-bitterbrush type. This type, even in its undisturbed condition, is far from ideal habitat, because the understory of perennial grass is generally not very dense and the grass dries early in the season. Meadow mice normally inhabit areas occupied by dense grass and herbaceous vegetation where some parts of the plants remain green during most of the growing season. Areas reseeded to bitterbrush (Purshia tridentata) are even less suitable for meadow mice than natural bitterbrush stands because site preparation for reseeding greatly reduces the understory. Nevertheless, in 1957 and 1958 meadow mice girdled bitterbrush plants in natural stands and one reseeded stand. The reseeded area in which the damage was found is located near Hallelujah Junction, in Lassen County, California. A hot wildfire had gone through the area in the summer of 1954 and it was reseeded to bitterbrush in the fall of 1954 and the spring of 1955. Initial stocking on the area was variable, ranging from about 150 to a little less than 1,100 seedlings per acre. These plants were subjected to extremely heavy use by jackrabbits and cattle, and many of them succumbed. To find out what the growth of the bitterbrush plants