for National Geographic News
They may not experience hot flashes, mood swings, or migraines, but female gorillas reach menopause just like human women do, according to a new study of gorillas at 17 U.S. zoos.
"Menopause has typically been viewed as a strictly human phenomenon," said Sylvia Atsalis, a primatologist at Brookfield Zoo in Chicago, Illinois, who co-directed the study. "Now we know that may not be the case."
The findings may not only improve the care of aging female gorillas but could also shed light on the human female reproductive cycle.
"Our findings underscore the similarities between humans and gorillas, our evolutionary cousins, who may be good models for an improved understanding of menopause [in humans]," Atsalis said.
The study began in 2002 as a pilot project at Brookfield Zoo.
Atsalis and a colleague, Sue Margulis, now a curator of primates at Chicago's Lincoln Park Zoo, wondered whether a gorilla named Alpha, born in 1961, should be given contraceptives to prevent her from becoming pregnant.
She showed considerable sexual interest in Ramar, the group's silverback. Once a month she would sit and stare at him intently, toss hay, and even attempt to sit in his lap.
But zoo staff feared that Alpha wouldn't be able to properly care for a baby because of her age.
Gorillas in zoos can live to be 50 or older, but females very rarely have babies after age 37.
The study that began with Alpha soon expanded to include 30 aging female gorillas at 17 zoos around the country.
The researchers tracked the hormonal cycles of the females by collecting fecal samples to check the levels of progesterone, a reproductive hormone.
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