Serum concentrations of oestradiol and progesterone during the normal oestrous cycle and early pregnancy in the lion (Panthera leo)

Abstract

During a 6 mo. study period weekly serum samples demonstrated 9 estradiol surges above 14 pg/ml (range 19-108 pg/ml) among 3 lionesses isolated from male lions. Intervals between peaks ranged from 3-8 wk. Progesterone surges of more than 17 ng/ml (range 17-282 ng/ml) and lasting for 2-6 wk were recorded after 7 of the estradiol peaks. Sexual behavior correlated well with the estradiol peaks. Except for cornification following estradiol peaks, there was no obvious vaginal cytology pattern at other times of the cycle. Pregnancy occurred after a 12 h contact with a male during behavioral estrus. During gestation (108 days) estradiol values remained low, while progesterone was elevated to 49 ng/ml within 12 h after mating, reaching a peak of 143 ng/ml at the 4th wk, and remaining elevated during the next 2 mo.