Serum concentrations of oestradiol and progesterone, and sexual behavior during the normal oestrous cycle in the leopard (Panthera pardus)

Three mature nulliparous female leopards were studied for 5 years. During three separate 6-month periods serum oestradiol and progesterone concentrations were measured at weekly intervals. Oestradiol was elevated over 21 pg/ml for 54 weeks during these 3 periods, and 36 oestradiol peaks (65.8 ± 6.3 pg/ml (mean ± s.e.m.), range 21-172 pg/ml) were identified. Daily frequency of feline reproductive behaviours averaged over each week increased from 1.9 ± 0.2 (n = 93) during weeks with low serum oestradiol concentrations (< 21 pg/ml) to 5,3 ± 0.6 (n = 54) during weeks when serum oestradiol concentrations (> 21 pg/ml) were high. Increased serum progesterone concentrations (13-98 ng/ml) were observed on 5 occasions in 21 leopards housed together. These presumptive luteal phases lasted from 1 to 5 weeks. Baseline progesterone values were 1.6 ± 0.4 ng/ml (n = 131). No progesterone increments were observed in isolated animals, and serum concentrations remained at baseline levels. These limited observations suggest that female leopards do not require intromission to induce ovulation and luteal function. The average interval between oestradiol peaks for cycles with no progesterone increment was 3.4 weeks (range 1-6 weeks). The interval for the 3 complete cycles associated with elevated progesterone concentrations was 7.3 weeks. Analysis of sexual behaviors over the 5-year study period revealed no evidence of seasonality in these captive leopards.