REPRODUCTION AND GROWTH IN THE CREEPING VOLE, MICROTUS OREGONI SERPENS MERRIAM

Abstract

The growth and reproduction of the cricetine rodent, Microtus oregoni serpens Merriam, has been studied in the laboratory and in the wild. Growth data arise largely from 28 captive born litters. It has been determined that gestation is [Formula: see text] to 25 days; that mean litter size is 2.95; that a postparturient oestrus is usual but frequently does not occur; that puberty occurs at 22–24 days in females and 34–38 days in males; that there is a sterile period of 5 to 14 days between first oestrus and first conception; longevity in captivity exceeded 320 days but in the wild there was a complete annual turnover. Instantaneous relative growth rates have been determined for four distinguishable phases of growth. A limited experiment using light and heat to stimulate increased reproduction had equivocal results.