 Stoats are not monogamous, with litters often being of mixed paternity.Stoats undergo embryonic diapause, meaning that the embryo does not immediately implant in the uterus after fertilization, but rather lies dormant for a period of nine to ten months.The gestation period is therefore variable but typically around 300 days, and after mating in the summer, the offspring will not be born until the following spring – female stoats spend almost all their lives either pregnant or in heat.