Once Feared Extinct, 1,329 Pea-Sized Snails Have Been Released on an Atlantic Island After Captive Breeding Effort

Just a few years ago, the outlook for island snails on the Portuguese Madeira archipelago appeared grim, at best. These animals were buckling under extinction pressures, and several species hadn’t been observed for more than a century. Biologists thought those snails had all but disappeared, with only empty shells and fossils left as evidence that they ever slid across the Earth.

Now, the fates of those snails have taken a positive turn: In the last decade or so, scientists found live members of species long thought to be extinct on the islands, kicking off a flurry of rescue initiatives for these floundering mollusks. In the latest page of their story, a massive rewilding effort has released more than 1,300 captive-bred snails onto wild ground. It marks a new chapter of survival—and a second lease at life—for the rare, endangered snails.

Scientists have a term for animals found alive after their kind was thought to have gone extinct: Lazarus species, named after the biblical figure from the New Testament who was resurrected. The discovery of some Madeira snails to be alive and breathing, in a way, felt similarly miraculous to conservationists.

A few years ago just 60 Desertas island land snails survived… but we’ve JUST reintroduced 1,300 to the wild

For 100+ years, they were thought to be extinct… then came a remarkable discovery! Just 60 were found on a tiny island in the Atlantic Ocean

They were flown to… pic.twitter.com/gK0n9JuS5c

— Chester Zoo (@chesterzoo) December 28, 2024

The Desertas Islands lie off the coast of Morocco and make up part of Madeira, like a row of jagged teeth sprouting up from the Atlantic Ocean. With steep cliffs and scant tree cover, the mountainous and windswept terrain might seem hostile to the tiny, shell-toting inhabitants there, but nature’s challenges are nothing compared to the threats that humans have introduced. Invasive species such as goats have annihilated local vegetation. Mice and rats have also feasted on the snails, tanking their population.

Despite these hurdles, the snails somehow managed to cling to survival. Researchers at the Institute for Nature Conservation and Forests (IFCN) in Madeira led expeditions between 2012 and 2017 and discovered a trove of 200 snails representing two endangered species on Deserta Grande, the largest of the Desertas Islands.

Worried the snails were the last of their kind, the researchers brought the shell-toting creatures into captivity in several zoos across the United Kingdom and France.

One of the sanctuaries was Chester Zoo in England. From a pool of 60 of the snails, the staff embarked on a mighty journey to parse their biological secrets, including how to multiply their numbers.

“It was a huge responsibility to begin caring for them,” says Gerardo Garcia, Chester Zoo’s head of ectotherms, per the Guardian’s Mattha Busby. “As a zoo conservation community, we knew nothing about them. They’d never been in human care before, and we had to start from a blank piece of paper and try to figure out what makes them tick.”

The zookeepers spent “countless” hours caring for each individual, he adds, and now, all that effort has paid off. A total of 1,329 of the snails’ offspring were released onto Bugio, another of the Desertas Islands. Unlike Deserta Grande, Bugio is free of goats and rodents, thanks to eradication interventions. Before the snails’ release, the researchers dotted their shells with an ultraviolet marker for easier tracking later on.

“For 100 years we thought they’d gone forever, but now there’s new hope,” says IFCN conservationist Dinarte Teixeira, who was involved in the first discovery of the snails, per the Agence France-Presse. “We’re striving to do everything we can to give them the best possible chance for the future.”

These dull-colored snails, no bigger than a pea, might not be much to look at, but they constitute important members of a healthy ecosystem. They’re a key food source for the native fauna, and they feed on dead plants, thus helping with nutrient cycling and soil fertility for other plants to grow robustly. As some students once described, snails “poop out fertilizer packets,” reported Joshua Rapp Learn for the Wildlife Society in 2021.

“All of that is dependent on the little guys—the insects and the snails that so often get overlooked,” Heather Prince, an invertebrate specialist at Chester Zoo, tells Victoria Gill of BBC News.

Snails are particularly vulnerable to environmental threats. Their slow-moving lifestyle means they are limited to narrow geographic areas, leaving them susceptible to the dangers of habitat loss. Island snails also evolved when their homes were free of predators, so they typically have few defenses against new invaders.

But, given their relative insulation from the outside world, islands have become biodiversity hotspots for snails. Half of all documented land snail species live on islands, and among these roughly 11,000 species, another half dwell on only seven islands. The Madeira archipelago harbors more than 320 land snail species, with most of them found nowhere else in the world. But worldwide, land snails constitute some 40 percent of all animal extinctions since 1500.

The Madeiran snails may yet escape this dire fate. Four additional snail reintroduction projects in the Desertas Islands are slated for this year and 2026. In the meantime, the researchers will monitor the snails’ survival rate to gauge the success of the current rewilding effort.

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

Shi En Kim | | READ MORE

Shi En Kim is a Washington, D.C.-based freelance science journalist. Her work has appeared in National Geographic, Scientific American, the Atlantic, Popular Science and others. In 2021, she interned at Smithsonian magazine as an AAAS Mass Media Fellow.