The Retention Time of Placental Spots in Tundra Voles (Alexandromys oeconomus)

To elucidate the resorption time of placental spots in tundra voles ( Alexandromys oeconomus Pall.) inhabiting the north taiga subzone, experiments were performed in the vivarium of the Institute of Biology of the Komi Scientific Center, Ural Branch, Russian Academy of Sciences, using 84 animals. The results show that implantation traces in the uterus in females with one litter remain 2 months, while in females who had repeatedly given birth, the resorption of placental spots starts 30–40 days after birth. Based on the studies, repeated pregnancy in tundra voles can be concluded to speed up the resorption of spots. The maximum period of the retention of placental spots in tundra voles is 4.5 months. Therefore, the placental spots in this species become dissolved significantly faster than in many other rodents, thus limiting the use of the technique for calculating the placental spots. Moreover, it is impossible to determine the number of litters in tundra voles by calculating the placental spots.