The zoo has been working for decades to preserve the tiny Partula nodosa snail, one of several species driven out of their native South Pacific habitat by efforts to control another invasive snail species that went awry.
In 1989, the Detroit Zoo said it got 115 individual snails from five related snail species. The zoo got other institutions to focus on four species and concentrated on breeding Partula nodosa snails.
At one time, the Detroit Zoo had all the known Partula nodosa snails in the world.
"Our efforts and successful breeding of the snails resulted in the rescue and recovery of the species," Scott Carter, the zoo's chief life sciences officer, said in a statement. "Currently there are six thousand individuals living in North American zoos, all descendants from the Detroit Zoo's original small group."
The disappearance of the species and its cousins in the wild was a result of an effort at biological control of giant African land snails, which were introduced to Tahiti and other south Pacific islands in 1967 as a human food source for people, the zoo said. It said some escaped, bred rapidly and began eating farmers' crops.
To control the African snails, Florida rosy wolf snails were introduced about 10 years later, but the wolf snails instead developed a taste for the Partula nodosa and its cousins, the zoo said.
"With the sufficient growth of the captive population and the establishment of a protected area on Tahiti, this species is officially on the road to being saved," Carter said.