Mountain Gorillas Reproduction and parenting: Females mature at 10–12 years (earlier in captivity), and males at 11–13 years. A female’s first ovulatory cycle occurs when she is six years of age, and is followed by a two-year period of adolescent infertility. The estrous cycle lasts 30–33 days, with outward ovulation signs subtle compared to those of chimpanzees. The gestation period lasts 8.5 months. Female Mountain gorillas first give birth at 10 years of age and have four-year inter birth intervals. Males can be fertile before reaching adulthood. Gorillas mate year round. BOOK NOW
Females will pursue their lips and slowly approach a male while making eye contact. This serves to urge the male to mount her. If the male does not respond, then she will try to attract his attention by reaching towards him or slapping the ground. In multiple-male groups, solicitation indicates female preference, but females can be forced to mate with multiple males. Males incite copulation by approaching a female and displaying at her or touching her and giving a “train grunt”. Recently, gorillas have been observed engaging in face-to-face sex, a trait once considered unique to humans and bonobos
Parental care of Gorillas
Since mortality is as high as 38% in mountain gorillas during the infancy period (from birth to three years), caregivers, primarily females, are acutely important in the survival of their infants. Because of their long period of development and dependence, gorilla mothers can expect to invest years caring for their vulnerable offspring. Although male gorillas do not take an active role in caring for infants, they play an important role in their socialization, often associating with older infants and juveniles. The relationship that develops between the silverback and infants in his group is usually supportive; he serves as an attachment figure during the difficult time of weaning and he shields young gorillas from intergroup aggression by intervening in disputes involving older, more dominant individuals. The silverback has a largely supportive relationship with the infants in his troop and shields them from aggression within the group. Infants remain in contact with their mothers for the first five months and mothers stay near the silverback for protection Infants suckle at least once per hour and sleep with their mothers in the same nest.
For the first five months of life, infant mountain gorillas remain in constant contact with their mothers and females seek close proximity to their resident silverback for protection. During this period, infants are dependent on their mothers for food, suckling at least once per hour, and sleep at night in their mothers’ nests. After five months, mother-infant pairs break body contact, but only for a few seconds and by 12 months, infants venture up to, but never more than, five meters (16.4 ft) away from their mothers. By 18 to 21 months, this distance between the pair is regular and increases. Concurrent with this decrease in proximity is a decrease in nursing frequency, with infants only nursing once every two hours. By the age of 30 months, infants spend only half of their time with their mothers.
The juvenile period is from three to six years and is characterized by a decrease in maternal grooming, no longer sharing a sleeping nest with the mother, and weaning. Because of the enormity of the task of rearing infants and the stress of lactation on the mother’s body, female gorillas experience lactational amenorrhea until the infant is weaned at three or four years. After the infant is weaned, the mother begins to ovulate and shortly thereafter becomes pregnant. Weaning conflict is minimized in gorillas, compared to other great apes, because of the cohesive nature of gorilla groups. The constant availability of play partners (including the silverback) may contribute to less intense conflict between mother and infant during this period.