Effects of uterine position on rate of sexual development in female Mongolian gerbils.

Examination of the rate of sexual maturation of 79 female gerbils from 32 Caesarean-delivered, foster-reared litters revealed that those females that, as fetuses, occupied uterine positions adjacent to one or two males (1M and 2M females) were less likely than those females occupying uterine positions not adjacent to males (0M females) to exhibit early vaginal opening. Our data further indicated that the uterine environment provided by late-maturing female gerbils biased their fetal daughters to themselves be late maturing to a greater extent than the daughters' uterine positions could explain. Daughters of late-maturing females in 1M and 2M uterine locations were more likely to be late-maturing than were daughters of early-maturing females in similar uterine locations. Because in female Mongolian gerbils age at vaginal opening is a powerful predictor of future reproductive strategy, the present results indicate that in female gerbils both prenatal maternal influence and uterine location are important determinants of future reproductive behaviors.