Tiny Snails Once Thought Extinct Are Returning Home Thanks to Zoo Conservation Efforts

Sometimes the biggest conservation victories come in the smallest packages.

Conservationists have successfully returned hundreds of critically endangered land snails to a remote Atlantic island after an international breeding program rescued four species that were on the brink of extinction. Among them is Geomitra coronula, a species that, just a few years ago, was represented by only 21 surviving individuals found beneath a single rock.

The remarkable reintroduction marks an important milestone for global conservation efforts and demonstrates how zoos are playing an increasingly important role in preventing species from disappearing forever.

A Species Reduced to One Rock

The tiny snails—each measuring less than 8 millimeters—are native to Bugio Island in Portugal's Desertas Islands archipelago.

Over centuries, introduced goats, rabbits, and mice devastated the island's native vegetation. With little fresh water available, invasive mice turned to the moisture-rich snails for survival, driving several species to the edge of extinction. By the time conservationists intervened, Geomitra coronula had been reduced to just 21 known individuals, all found sheltering beneath a single rock.

Zoos Step In

Recognizing the urgency, the Madeira government partnered with Chester Zoo in the United Kingdom and ZooParc de Beauval in France to establish emergency conservation breeding programs.

Researchers first had to solve a unique challenge: almost nothing was known about caring for these species in captivity. Specialists developed husbandry techniques from scratch, determining the snails' preferred diet, environmental conditions, and breeding requirements.

The effort paid off.

Today, more than 300 captive-bred Geomitra coronula and 270 Discula lyelliana have been successfully returned to Bugio Island, while additional breeding colonies continue to safeguard the remaining species involved in the project.

A Difficult Journey Home

Returning the snails to the wild was anything but simple.

Bugio Island has no dock, requiring conservationists to jump from boats into the ocean before climbing steep cliffs carrying containers filled with the tiny mollusks. To protect the island's rare seabirds, the team conducted much of the work at night using red-spectrum lights rather than bright white flashlights.

Despite the logistical challenges, the releases have exceeded expectations.

Monitoring suggests the captive-bred snails are surviving well and beginning to establish new wild populations.

Why Tiny Snails Matter

Although easy to overlook, land snails play an essential ecological role.

They help break down plant material, recycle nutrients, improve soil quality, and contribute to healthy ecosystem function. Restoring these species may accelerate recovery of Bugio Island's fragile habitat following years of invasive species removal and restoration efforts.

Conservationists hope the returning snail populations will help rebuild the island's natural ecological processes while supporting broader biodiversity recovery.

A Win for Conservation Zoos

The project highlights the growing role modern zoos play beyond public education.

Facilities like Chester Zoo and ZooParc de Beauval increasingly serve as conservation centers, maintaining assurance populations of critically endangered species, developing breeding protocols for little-known animals, and partnering with governments to reintroduce wildlife into restored habitats.

For Geomitra coronula, whose entire global population once fit inside a single petri dish, that work may have prevented extinction.

The successful reintroduction offers a hopeful reminder that, with collaboration, habitat restoration, and science-based conservation, even species on the very edge of disappearing can be given a second chance.