Wildlife conservationists are celebrating a big milestone reached by a little black-footed ferret and her offspring, born at the Smithsonian National Zoo and Conservation Biology Institute earlier this year.

The significance of two healthy ferrets born to Antonia, a cloned female, "cannot be overstated" in the world of wildlife conservation, said Ben Novak, lead scientists for Revive & Restore, a biotechnology company that collaborated with the Smithsonian. Because black-footed ferrets are endangered, "this represents a number of world firsts," Novak said, and hopefully, the kits will contribute new genetic diversity to the species.

"It's the first cloned black-footed ferret to have offspring, but also the first clone of any endangered species to produce offspring to help save their species," Novak told USA TODAY.

The Smithsonian National Zoo did not respond to a request for comment.

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The successful reproduction of a clone is a landmark "proving that cloning technology can not only help restore genetic diversity but also allow for future breeding, opening new possibilities for species recovery," the U.S. Fish and Wildlife Service said in a news release this month.

The kits are a female named Sibert and a male called Red Cloud. They were born in June, along with a third who died shortly after birth, according to the agency.

Sibert and Red Cloud could make an enormous contribution to the species because their mother was cloned from a black-footed ferret from the 1980s, named Willa, who had no offspring. Because Willa is unrelated to all other black-footed ferrets alive today, her DNA was previously "completely lost" the black-footed ferret population.

All other black-footed ferrets in the U.S. are descendants of just seven other animals, and Willa's biological samples contain "three times" the genetic diversity held in the black-footed ferret population, the U.S. Fish and Wildlife Service said.

"It's the first time people have been able to reach back into the past and restore lost genetic variation with a female," Novak said.

A couple of other black-footed ferrets have been cloned from Willa in recent years, but Antonia, who was born last year, is the only to have offspring.

Novak told USA TODAY that Antonia independently chose her mate, a 3-year-old named Urchin, and said he is "absolutely thrilled" about Sibert and Red Cloud. The new kits are now nearly 5 months old and the official announcement of their birth was delayed until Nov. 1 to ensure they were in good health, he said.

"It doesn't matter if we make a thousand clones, if none of them have babies it never reached the goal, so these two babies are such a pivotal landmark moment in history," Novak said.