Pregnancy failure in female prairie deermice related to parity and social environment

Abstract

The occurrence of ‘pregnancy block’ was noted in nulliparous and recently parous female prairie deermice when exposed to one of the following situations during a period from 24 to 72 hr subsequent to insemination: (1) stud male removed and female left alone, (2) stud male left with female, (3) stud male removed and strange male placed with female and (4) strange male placed with female and stud male. All females were killed at 10 days post-insemination and examined for embryos. There was a significantly greater frequency of pregnancy among parous females than nulliparous, although age differences may have been an important confounding variable. Further, there were decreasing pregnancy proportions in both parous and nulliparous females in the treatment sequences of (2) stud male left with female, (1) stud male removed and female left alone, (4) strange male placed with female and stud male and (3) stud male removed and strange male placed with female.