Over 1,300 critically endangered, pea-sized snails, bred in captivity, have been released onto a remote Atlantic island to reclaim their natural habitat.

This release reintroduces two species of Desertas Island land snails to the wild, previously thought extinct for over a century. Conservationists rediscovered a small population on the rocky cliffs of Deserta Grande, near Madeira, prompting a rescue mission.

The snails were transported to zoos in the UK and France, including Chester Zoo, where they were housed in a specially adapted shipping container. Conservationists recreated the snails’ natural habitat with miniature tanks, providing suitable vegetation and conditions.

The snails, native to Deserta Grande’s windswept, mountainous terrain, had faced habitat destruction caused by invasive rats, mice, and goats brought by humans. These predators were believed to have driven the snails to extinction until conservation expeditions between 2012 and 2017 uncovered about 200 surviving individuals.

Deemed the last of their kind, the snails were collected for a captive breeding program. Chester Zoo’s conservation science team cared for 60 snails, successfully breeding 1,329 offspring. Each was marked with identification dots using non-toxic pens and nail varnish before being returned to the wild.

“[It’s a] colour code,” said Dinarte Teixeira, a conservation biologist at Madeira’s Institute for Nature Conservation and Forests. “This will allow us to spot them and track where they disperse to, how much they grow, how many survive and how well they adapt to their new environment.”

The snails were released on Bugio, a smaller island in the Desertas archipelago, where invasive species have been eradicated, and the habitat restored. Bugio, now a nature reserve, offers a safe refuge for these tiny mollusks.

Gerardo Garcia of Chester Zoo described the reintroduction as “a major step in a species recovery plan,” underscoring the importance of this effort in preventing extinction.

“If it goes as well as we hope, more snails will follow them next spring. It’s a huge team effort which shows that it is possible to turn things around for highly threatened species.”

“These snails are such an important part of the natural habitat [on the islands they come from],” explained Heather Prince from Chester Zoo. As well as being food for other native species, she explained, snails break down organic matter and bring nutrients to the soil.

“They help plants grow. All of that is dependent on the little guys – the insects and the snails that so often get overlooked.”

This initiative demonstrates the critical role of conservation in preserving biodiversity and restoring ecosystems.