These Tiny Snails Are Breeding in the Wild for the First Time in 40 Years in French Polynesia

In French Polynesia, tiny snails are making a big comeback.

For the first time in nearly 40 years, researchers have discovered adult Polynesian tree snails that were born in the wild, according to a statement from the London Zoo.

The gastropods—a species called Partula tohiveana—had previously been considered extinct in the wild. But thanks to a global effort to save and reintroduce them, the snails appear to be regaining a foothold within the islands in the South Pacific.

Each year for the last decade, biologists have been flying thousands of zoo-born snails to French Polynesia and letting them loose. To keep tabs on the reintroduced snails, researchers mark their shells with a dot of UV-reflective paint that makes them more visible at night, when they’re most active.

Partula snail species now reestablished in the wild

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This year, at the beginning of September, scientists once again made their annual journey—with the snails in tow. They released more than 6,000 snails, all belonging to species and subspecies of the Partula genus, on Mo’orea, Tahiti and Huahine, three of the 118 islands that make up French Polynesia.

While on Mo’orea, they discovered unmarked Partula tohiveana in the wild—snails that didn’t have the UV-reflective paint on their shells. That’s a positive sign, as it means the snails are breeding on their own in the habitat.

“This is the kind of news that you work your whole career for,” says Kayla Garcia, zoological manager of invertebrates at the St. Louis Zoo, one of the institutions working to save Partula snails, to KSMU’s Miya Norfleet and Emily Woodbury. “This is an amazing discovery, an amazing accomplishment, and you can’t just can’t help but just feel all of the good feelings coursing through you.”

Conservationists say they will now start the process of getting the snails downlisted from “extinct in the wild” to “critically endangered” with the International Union for Conservation of Nature (IUCN).

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Partula snails are diminutive, measuring less than an inch long, but they play an important ecological role on French Polynesia’s tropical islands. They chow down on decaying plant matter and fungi, which helps keep the forest healthy. Partula snails are also part of Polynesian culture, as “the shells of each species represent the cultural identity of each island,” per the Zoological Society of London.

But why did Partula snails disappear in the first place? In 1967, French authorities allowed captive, non-native African giant land snails to be brought to the islands to provide food for human residents.

This effort didn’t go exactly as planned: The snails escaped into the wild, multiplied and wreaked havoc on the islands’ fragile ecosystem. The large, invasive mollusks, which can grow up to eight inches long, feed on more than 500 plant species—including crops. They also eat stucco on homes (to get calcium for building their shells) and can carry a harmful parasite that can cause meningitis in humans.

African giant land snails are difficult to curb, because they reproduce quickly and abundantly. A single snail can lay up to 2,500 eggs in a single year.

In a bid to stop them, authorities released another snail in French Polynesia: the rosy wolf snail. These carnivorous creatures—known as “cannibal snails”—were supposed to hunt and eat the African giant land snails. But, instead, they went after smaller, slower species of native snails. The rosy wolf snails drove many snails, including several species of Partula, to the brink of extinction. At least 51 of the 77 known Partula species were completely wiped out.

In the early 1990s, biologists at the Edinburgh Zoo and the London Zoo gathered up the few surviving Partula snails they could find in French Polynesia. They brought the animals back to their facilities, recruited other zoos in the United Kingdom and the United States to help, and kicked off a global captive breeding program to keep the species alive.

In the years since, the captive breeding program has produced a bit of a mixed bag of results. Some snail species thrived in captivity, while others did not reproduce. For example, in 2016, the last Partula faba snail on the planet died at the Edinburgh Zoo.

But, in total, scientists at the 15 partnering zoos have saved several species and subspecies and have now reintroduced more than 30,000 individuals into the wild.

Very few extinct-in-the-wild species become successfully reestablished, so Partula tohiveana’s recent comeback is especially rewarding. To conservationists, the Partula initiative is a “powerful example of how conservation zoos can combat biodiversity loss,” says Paul Pearce-Kelly, senior curator of invertebrates at the London Zoo, in the statement.

“At a time when nature faces unprecedented challenges, these small snails are a symbol of hope for global wildlife,” he adds.

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.