Animal conservation experts in the United Kingdom and Portugal praised a breeding program that saved two critically endangered snail species, resulting in the release of 1,329 individuals on a remote island in the Atlantic Ocean.

The wild snails on the Desertas Islands were thought to be extinct, as none had been seen for over a century. However, conservation experts discovered a small group of them on the nearby island of Deserta Grande, near Madeira, in 2017.

Expected to be the last remaining group of this small species, a team from the Institute for Nature Conservation and Forests sent 60 snails to Chester Zoo in northwest England. There, specialists provided the ideal conditions for the snails to thrive and successfully bred them for the first time ever under human care, according to the zoo.

Some of the snails from Chester Zoo were also sent to two leading European conservation zoos: one in Bristol, England, and another in Beauval, France, which doubled their numbers.

After these successes, viewed as a model for other conservation efforts, 1,329 snails were returned to the nearby Bugio Island. This small, protected island in the North Atlantic was chosen because it was free of invasive goats, rats, and mice—the main threats that had nearly wiped out the snails.

“When the snails were first brought to Chester, the future of this species was in our hands,” said Gerardo Garcia, head of the Ectotherms Department at Chester Zoo, describing it as “a heavy responsibility.” He added, “These snails were really on the verge of extinction, and the fact that we have managed to give them a chance to come back is thanks to the efforts of many people.”

The snails released on Bugio have been marked with a uniform color, allowing for close monitoring on the island. If the release is successful, more snails will be added to provide an additional boost to the species.