Relationship between fecal estradiol and progesterone concentrations and reproductive startup in female red pandas (Ailurus fulgens)

By radioimmunoassays, we analyzed fecal estradiol (E2) and progesterone (P) concentrations of four female red pandas (Ailurus fulgens ) from Chengdu Zoo and Chengdu Research Base of Giant Panda Breeding from December 1999 to April 2000. Meantime, we investigated mating activity of the red pandas. The results showed that there was a rapid increase in E2 concentration, accompanying several peaks. This implied that female red pandas might be seasonally polyestrous. Before mating, E2 concentration reached the peak, meanwhile, P concentration also increased. This indicated E2 and P were both important factors for promoting the female's mating activity. The copulation couldn't occur when E2 concentration reached the peak without P concentration increase, which was a dark rut. P concentration increasing continually after mating, presumably, an ovulation phenomenon had occurred according to the female's kittening later. This implies that the ovulation mode of red pandas primarily is inductive, and the inductive factor is mating stimulation