A gorilla at Zoo Atlanta has given birth to twins — only the sixth time that's happened in a North American zoo since 1966.

Zoo officials say Kuchi (search), a 21-year-old female western lowland gorilla (search), gave birth to twins on Monday. The twins are the first offspring of Zoo Atlanta's newest silverback, Taz (search), and the third and fourth offspring for Kuchi.

"The Zoo Atlanta family is elated at the news of twin gorilla babies," Dennis Kelly (search), Zoo Atlanta president and CEO, said in a news release. "We are proud to do our part to support a species that is experiencing such catastrophic decline in the wild."

There are about 350 western lowland gorillas in captivity in North America.

Experts say fewer than 75,000 survive in the wild, partly because their habitat is being destroyed by logging and farming. The illegal bushmeat (search) trade in Africa, where wild animals are slaughtered for human consumption, is another reason.

Zoo Atlanta's team of primate experts and veterinary staff plan to monitor Kuchi and the twins closely. Of the six sets of twins born since 1966, only three survived.

"Kuchi is a proven mother; however, the next 48 hours will be crucial to the twins' survival," said Dr. Tara Stoinksi, manager of conservation partnerships at the zoo.

Fifteen gorillas have been born and raised at Zoo Atlanta since 1988. With 22 western lowland gorillas, Zoo Atlanta has the second-largest collection in North America. And officials say an additional three gorillas at the zoo are expecting.