ASHEBORO, N.C. -- The North Carolina Zoo has announced that one of its gorillas, Rosie, has died.

• Rosie was a 43-year-old western lowland gorilla.
• Seven gorillas remain in the NC Zoo's troop.
• Western lowland gorillas are critically endangered.

The zoo says Rosie was a 43-year-old female western lowland gorilla and a matriarch of the zoo's troop.

After developing an aggressive abdominal mass that was inoperable due to her old age, she was humanely euthanized last Thursday.

According to the zoo, the life expectancy for female gorillas is 38 and a half years old.

Born in 1974, she had several infant gorillas and was an “excellent surrogate mother” who “cared for offspring that were not her own.” She happened to be the mother of Timu, the country’s first and only gorilla born through in vitro fertilization. Officials say she was such a good surrogate mother, a 5-year-old juvenile gorilla, Dembe, was brought to the NC Zoo from Colorado after his father died.

She joined the gorilla troop at the NC Zoo in 2015 from Omaha with her grandson, Hadari, and a silverback, Mosuba, who was Timu’s sperm donor.

"Rosie was a feisty and at times cantankerous old lady, but she was well respected by her troop members and caretakers. She played an important role in AZA (Association of Zoos and Aquariums)'s gorilla population, fostering and caring for young gorillas throughout her life. Her impact will be long-standing,” said Jennifer Ireland, curator of mammals for the North Carolina Zoo. “

“Rosie was the grandma of the troop. To sum up Rosie in a few words is very hard to do. She was a very strong lady and very vocal – she always had something to say. All of us keepers will miss her tremendously,” said Jason Balder, a North Carolina Zookeeper.

Seven gorillas, including Dembe, Hadari and Mosuba, remain in the NC Zoo’s gorilla troop.

Western lowland gorillas are considered to be critically endangered because of their habitat destruction and poaching.