Prenatal Survival and Loss in Some Cricetid Rodents

Abstract

In spite of the fact that during recent years much stress has been placed upon the dynamic aspects of mammalian populations, very little is known about prenatal survival and loss. Detailed studies of prenatal mortality in North American wild mammals appear to have been limited to the brush rabbit (Mossman, 1955), mule deer (Robinette et al. , 1955) and meadow vole (Hamilton, 1941). The extensive work on the wild rabbit in England has been well reviewed by Brambell (1948). Other Old World studies include work on the brown rat (Perry, 1945), common shrew (Brambell, 1935), bank vole (Brambell and Rowlands, 1936), multi-mammate mouse (Brambell and Davis, 1941), and gray squirrel (Deanesly and Parkes, 1933). The estimates of intrauterine loss in these studies, depending on what information is available, varied from 9 to 43 per cent. This discussion presents data gathered in Minnesota between 1950 and 1955 on the meadow vole ( Microtus pennsylvanicus ), red-backed vole ( Clethrionomys gapperi ), woodland deer mouse ( Peromyscus maniculatus gracilis ) and the prairie deer mouse (P. m. bairdii ). All of the red-backed voles and woodland deer mice and part of the meadow voles were taken from the vicinity of Basswood Lake, Lake County, Minnesota, and all of the prairie deer mice and most of the meadow voles were taken from the Rosemount Agricultural Experiment Station in Dakota County, Minnesota. The collecting of material at Basswood Lake was partially supported by the Quetico-Superior Wilderness Research Center. This contribution is Paper No. 3548, Scientific Journal Series, Minnesota Agricultural Experiment Station, St. Paul, Minnesota. In order to make a thorough analysis of intrauterine mortality rates it is necessary to know the number of ova ovulated, the number that are fertilized, the number of zygotes that implant and the number of embryos that survive to parturition. Our data only partially fulfill …