Why are 1,329 baby snails released on a remote island?

More than 1,300 endangered, pea-sized snails bred by a zoo have been released to wander (very slowly) on a remote island in the Atlantic Ocean.

This release results in two species of wild snails on Desertas Island returning to the wild. Before that, they were thought to be extinct, and neither species had been spotted for a century.

When a team of conservationists found a small group of the organisms on the rocky cliffs of Deserta Grande Island, near Madeira, they launched a rescue effort.

The snails were brought to zoos in the UK and France, including Chester Zoo, where they were made a home in a converted shipping container.

These small molluscs are native to the mountainous, windswept island of Deserta Grande, southeast of Madeira. The habitat there has been destroyed by rats, mice and goats brought to the island by humans.

All of these invasive predators were thought to have eaten the tiny snails to extinction. Then a series of conservation missions – between 2012 and 2017 – proved otherwise.

Conservationists have discovered only 200 individuals alive on the island.

These snails are believed to be the last of their kind, so they were collected and brought into captivity.

At Chester Zoo, the conservation science team has built a new home for 60 precious snails. Appropriate food, plants and conditions have been recreated in miniature habitat tanks.

The 1,329 snail offspring, raised at the zoo, have now been tagged with identification points – using non-toxic pens and nail polish – and transported back into the wild for release.

“(It is) a color code,” said Dinarte Teixeira, a biologist at the Madeira Institute for Nature and Forest Conservation. “This will allow us to detect them and track where they are spreading, how much they grow, how many survive and how well they adapt to their new environment.”

A wild refuge for the snails has been restored on Poggio, a smaller neighboring island in the Ilhas Desertas (Desert Islands) archipelago.

Bugio is a nature reserve and invasive species have been eliminated there.

Gerardo Garcia of Chester Zoo said the reintroduction was a “huge step in the species' recovery plan.”

“If things go as we hope, more snails will follow next spring. It's a huge team effort that shows it is possible to turn things around for critically threatened species.”

“These snails are an important part of the natural habitat (on the islands they come from),” explained Heather Prince from Chester Zoo. She explained that in addition to being food for other native species, snails decompose organic matter and bring nutrients to the soil.

“It helps plants grow. It all depends on the little ones – insects and snails that are often overlooked.”