Abstract
General pattern of growth and reproduction of a population of Clethrionomys gapperi in winter and spring was studied at Edmonton, Alberta, Canada. Subnivean growth was slow throughout winter and spring. After loss of snow cover in first week of April weight increased by about 30 percent in one month when first pregnancies occurred. Young of the year had not been captured as of the first week in June. Adaptive values suggested by others for this pattern of growth and reproduction are mentioned.