Plasma estrogen levels during delayed implantation in the European badger ( Meles meles L.)

Estrone (E 1) and estradiol (E 2) concentrations were determined in peripheral plasma of female badgers during delayed implantation (February through early January of the next year and at the time of implantation (usually in January). Estrogen levels were low during most of diapause. The concentration of estrone exceeded that of estradiol. However, fluctuations in estrogen levels occurred between May and October. Individual estrogen profiles revealed that the estradiol concentration increased significantly the last week of May ( P < 0.02), July ( P < 0.05), and September ( P < 0.001) and that the estrone level rose in July ( P < 0.05). Changes in estradiol secretion occurring at regular intervals confirm the existence of ovarian activity during delayed implantation as previously suspected.