Reproduction of the California red-backed vole in western Oregon

Two hundred and sixty Clethrionomys californicus specimens were collected in western Oregonfrom 1952 to 1965. The sex ratio of 258 animals was 49 percent males. The range of shortest bodylengths for fecund animals was 90 to 99 mm for males and 80 to 89 mm for females. Males werein breeding condition from February to October and females from April to November, based onthe combined years. Average number per set of corpora lutea was 2.86, placental scars 2.91, andembryos 2.63. Seventeen percent of the lactating females had postpartum pregnancies and thecalculated minimum number of litters per year was 3.1.