The hormonal induction of mating behavior in female gray short-tailed opossums (Monodelphis domestica).

The activating effects of estradiol alone and of estradiol plus progesterone on copulation and related behavior were examined in ovariectomized female gray short-tailed opossums. Following receipt of subcutaneous estradiol (E) or cholesterol (C) implants, E-females showed less screeching threat behavior toward intact males than C-females. Intact males showed more precopulatory behavior toward E- than toward C-females, and 20% of E-females and no C-females copulated with males. In a second experiment, females that had previously received subcutaneous E implants received injections of either corn oil alone (E + OIL) or 500 micrograms progesterone in corn oil (E + P) 4 hr before behavioral testing. Of E + P-females, 88% copulated with males, compared to 38% of E + OIL-females. All females that copulated in both experiments showed anogenital dragging just prior to copulation. Hormonal induction of estrous behavior and copulation has not been reported previously in a female marsupial.