Jenny, Shamba, Timbo, Beta, and Elaine are gorillas at the zoo, but they share a common trait with millions of women: they also experience menopause.
A study conducted on 30 gorillas across 17 zoos in North America has provided the first conclusions regarding menopause in this species. The results may help zoos improve the care of older female gorillas and alter biologists’ perceptions of menopause in humans.
“Do they experience hot flashes? Do they feel discomfort? We need more time to determine this,” said Sue Margolis, the study’s author at Lincoln Park Zoo in Chicago.
Many biologists believe that menopause evolved to allow grandmothers more time to care for their grandchildren, noted Steve Austad from the University of Texas.
However, the new findings challenge this notion, as female gorillas in the wild typically separate from their families rather than staying to care for their young. Instead of being an evolutionary adaptation, menopause simply allows these gorillas to live longer.
“This will cause evolutionary biologists to rethink their stance. Currently, they still consider humans to be unique. But gorillas may also live to be 75 years old, with the last 25 years being post-menopausal,” Austad remarked.
The oldest captive gorilla, Jenny, is currently 51 years old at the Dallas Zoo. She is one of the 30 gorillas included in the study and is among the 23% of older gorillas that are menopausal.
Another 32% showed abnormal hormone levels over several months, indicating they were approaching menopause. The average age of menopause in gorillas is 44, while in women it occurs around 51.
The study began when scientist Margolis was unsure whether to give Alpha, a 40-year-old gorilla at Brookfield Zoo, birth control pills while she remained interested in mating. Typically, birth control is administered to gorillas to manage reproduction.
Margolis tested Alpha’s hormone levels and found them sufficiently low, indicating that birth control was unnecessary. Gorillas have a monthly menstrual cycle with very little bleeding and mate year-round.
