Western Lowland Gorilla (Gorilla gorilla gorilla) Fact Sheet: Reproduction & Development

• Not observed for western gorillas in the wild.
• Females in Virunga National Park, Democratic Republic of the Congo, and in managed care have provided information on receptivity.
  • First mating ~7.5 years
  • First conception ~8.5 years
• Adult females mate with silverback on different days
• Copulations occur during travel-feed periods

Sexual Maturity: Age at first reproduction not yet measured at any Western site. Following data based on Mountain gorillas and gorillas in managed care.

• Male: Complete copulation by age 9-10 years but few mating opportunities until Silverback status ~ 12-15
• Female: Perineal tumescence observed in the field ~5.7-7.1 years
  After 2 years of adolescent sterility, first birth - 8.5-10 years.

Estrus cycle: estrus period = 1-2 days, 22-38 day cycle.
First pregnancy: 8.5-10 years
Gestation: 251-295 days
Young per birth: 1, twins rare
Reproductive Rate: 3.5 - 4.5 year birth interval
Infant mortality: varies depending on group 8%-43%

• Develop twice as fast as humans
• Infants (0-3 years)
• Crawl at 3 months
• Begin eating some plants at 2.5 months
• 4-6 months - run on all fours
• Climb at 6-7 months
• Weaning - 3 years+
• Juveniles (3-6 years)
• Sub-adults (6-8 years)
• Adult female > 8-10 years
• Blackbacks / adult males (8-11 years) Silvering of hair begins around age 10.
• 18 years to reach full maturity
• Young silverbacks (12-15 years)
• Silverbacks >15

Managed care

• Median life expectancy (AZA 2023)
  • Males: 32.7 years
  • Females: 39.1 years

Western Lowland Gorilla and infant.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

A three-week-old Western lowland gorilla observed his surroundings as he was held by his mother (San Diego Zoo, 2015).

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Robbins, (2004)
Maple & Hoff, (1982)
Watts, (1991)
Grzimek, (1990)
Fossey, (1982)