Everyone is familiar with the roe deer, either from crossword puzzles or from real-life encounters during a jog or a hike in the forest: majestic creatures with elegant big black eyes.
As common as roe deer may seem in Swiss forests, one of their characteristics is unique among deer species. After mating and fertilisation of the egg in midsummer, the pinhead-sized embryo does not implant in the uterus, but enters into a period of dormancy, called embryonic diapause. This period lasts for over four months until December. Only then does the embryo continue its development at normal pace and implants in the uterus. In May, after four and a half months of “real” gestation, the doe gives birth to one to three fawns.
Although the phenomenon has been known for more than 150 years, it still puzzles. Various forms of embryonic diapause are known to occur in over 130 mammalian species….
