Influence of snowcover on survival of Clethrionomys gapperi inhabiting the Appalachian and Rocky Mountains of North America.

Red-backed voles were live-trapped in a Colorado subalpine forest and in a deciduous forest of the Appalachian Mountains of Pennsylvania. On the rocky Mountain Site (RMS) snow covered the ground for 71/2 months, reaching a depth of 270 cm; on the Appalachian Mountain Site (AMS), snowcover was intermittent reaching a maximum depth of 30 cm. Minimum ambient temperature on both sites was -28oC. Density of C. gapperi on the RMS showed a high of 48 voles per ha in December and a low of 10 voles per ha in May. Density of voles on the AMS showed less fluctuation, with a high of 30 voles per ha in October declining to a low of 12 voles per ha in April. Two periods of high mortality existed for voles on the RMS corresponding to the time of fall freeze and spring thaw. On the AMS low survival was seen during spring but not associated with snowmelt.-from Author