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Circulating progesterone and oestradiol-17β concentrations in cyclic Cape porcupines, Hystrix africaeaustralis

Summary. The general pattern of steroid secretion during the 30-day oestrous cycle of the Cape porcupine is that of a surge (25–176 pg/ml) in oestradiol-17β secretion at the time of perforation of the vaginal closure membrane, followed by an increase in progesterone concentrations, the latter attaining peak values (mean 5·9 ± 2·1 ng/ml) 8–19 days (13·8 ± 2·8 days) after vaginal opening. Copulation occurred after the oestradiol-17β surge and the length of the luteal phase of the cycle varied from 21 to 35 days (29·3 ± 4·7 days), this representing 93% of the length of the cycle. Perforation of the vaginal closure membrane was not always accompanied by an increase in oestradiol-17β levels and some instances (19%) of vaginal opening were not followed by an increase in progesterone secretion. The hormonal characteristics of the oestrous cycle of females housed with vasectomized males were similar to those of females housed with intact males.