Males mature at about 12 years but seldom breed successfully before 15 years. B. Reproductive Cycles. The gorilla menstrual cycle is about 30 to 32 days long. Ovulation occurs mid-cycle during a 2 to 3 day period. Labial swelling during estrus is minimal, especially in comparison with a chimpanzee.
Gorillas breed throughout the year.
Immature males check a female for olfactory cues to estrus. A receptive female solicits the dominant silverback by special glances and touches. Only the dominant silverback breeds with adult females in estrus. He allows subordinate males to court immature or pregnant females. D. Captive Breeding.