Gorilla Reproduction Cycle and Parenting: Gorillas have a fascinating reproduction cycle and parenting. Similar to humans, gorillas have a slow reproduction, giving birth to only one baby at a time and then raising that infant for several years before giving birth to again.
This slow reproduction rate makes gorillas very vulnerable to any population declines.
Wild female gorillas give birth about once every four years, therefore they have no fixed breeding season. The gestation period is about eight and a half months, and births are usually single. Though birth of twins occurs, it is a rare occasion and considered a blessing.
A new born gorilla weighs only about 2 kg and is utterly helpless for the first three months of life, during which it is carried in its mother’s arm. They sleep in their mother’s nest at night and rides on her back during the day. Female gorillas begin to reach reproductive maturity at about 10 years of age and then transfer to another group or to a lone silverback.
Most male gorillas leave their maternal group in which they were born and try to gather females to form their own family group. This may involve conflict and some aggression, since a young male may invade an established group and try to kidnap females, sometimes killing the infants in the process.
Occasionally a male will stay in his birth group and become its second silverback, breeding with some of the females and ultimately taking over its leadership when his father ages or dies.
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 these 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 adult hood.
Gorillas mate year round
When female gorillas are ready to mate, they will purse their lips and slowly approach a male while making eye contact. This serves to urge the male to mount her and 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.
Gorilla babies/infants are vulnerable and dependent, thus mothers are their primary care giver and are very important to their survival. Male gorillas are not active in caring for the young, but they do play a role in socializing them to other youngsters.
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 begin to break contact with their mothers after five months, but only for a brief period each time. By 12 months old, infants move up to five meters (16 feet) from their mothers. At around 18-21 months, the distance between mother and offspring increases and they regularly spend time away from each other.
In addition, nursing decreases to once every two hours.
Infants spend only half of their time with their mothers by 30 months. They enter their juvenile period at their third years, and this lasts until their sixth year. At this time, baby gorillas are weaned and they sleep in a separate nest from their mothers. After their offspring are weaned, females begin to ovulate and soon become pregnant again.
The presence of play partners, including the silverback, minimizes conflicts in weaning between mother and offspring.
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The Life Expectancy of Gorillas
The life expectancy of wild gorillas is about 35 and 40 years, though gorillas in captive have a life expectancy of 50s, a female western gorilla at the Columbus Zoo and Aquarium was the oldest known gorilla, at 60 years of age when she died on January 17, 20017.
Summary Gorilla Life Cycle
A gorilla life cycle consists of growth and development as shown below
Stage 1: Infancy
The infancy stage is from 0 to 3 years. Gorillas are nursed by their mothers, and most of their time is spent with their mothers and are seen riding on their banks.
Stage 2: Juveniles
The juvenile stage is from 3 to 6 years. Gorillas become more adventurous in this stage and play a lot with their siblings helping them socialize.
Day 3: Sub-Adult
The sub-adult stage is from 6 to 10 years. Gorillas are very independent, socialize a lot with others, and females reach sexual maturity while males continue growing.
Stage 4: Adult
The adulthood stage of a gorilla is from 10 years and above. Males become black-backs with a dark coat, and the dominant males become silverbacks, with a silvery patch on their backs.
Lifespan of Gorillas
The average lifespan of gorillas is 35 to 40 years. However, they can sometimes live up to 50 years.
