Critically Endangered Snails Reintroduced to Norfolk Island

After being declared extinct for more than two decades, the Campbell’s keeled glass-snail (Advena campbellii) has been returned to its natural habitat on Norfolk Island in a landmark conservation effort.

Snail Thought Extinct Rediscovered in 2020

The species was officially listed as extinct on the International Union for Conservation of Nature (IUCN) Red List in 1996, alongside other iconic losses like the thylacine. But in 2020, Norfolk Island citizen scientist Mark Scott photographed an unusual large snail, alerting malacologist Dr Isabel Hyman at the Australian Museum. Hyman immediately recognised it as the long-lost Campbell’s keeled glass-snail.

“As far as I knew, it was extinct, so we were very excited,” Hyman recalls.

Later that year, Hyman and colleagues located the snails in a sheltered valley on Norfolk Island, hidden beneath decayed palm fronds.

Captive Breeding at Taronga Zoo

In 2021, 46 snails were transported to a captive breeding facility at Taronga Zoo, established as a lifeline for the species. The snails give birth to live young every fortnight, but early breeding efforts struggled to offset natural mortality, as the animals live about 12 months in captivity.

“We did have a lot of deaths among the founding snails initially,” Hyman says, adding that Taronga Zoo staff learned the species was particularly sensitive to both transport and stress from being handled.

Over two years, however, the population grew to more than 800 snails, enabling the team to plan what is believed to be Australia’s first large-scale snail translocation.

Early Setbacks and Mass Die-Off

PhD student and Australian Museum research associate Junn Kitt Foon arrived on Norfolk Island in May 2025 to monitor the snails during their release. The snails were first held in a dedicated facility to acclimate them to local food sources and conditions.

Despite surviving the 1,700km journey from Sydney, a mould outbreak in the holding tanks killed 260 of the 600 snails. Similar losses have occurred in previous snail reintroductions, so the team had contingency plans in place.

Snails Released into the Wild

“A lot of thought went into where we ended up putting the snails,” says Melinda Wilson, natural resources program manager at Norfolk Island national park. The existing population of Campbell’s keeled glass-snail is only found in a small gully of native forest, “but they used to be spread all over the park”, Wilson says.

The team chose a release site that best matched the original habitat’s temperature and humidity, in a steep, “beautiful valley surrounded by palm trees”, with native hardwoods providing shade. “To get down to it we had to cut a new line through thick guava, which is an invasive plant, to be able to get to this pristine valley,” Wilson says.

“It’s on the other side of the park,” she adds. “I don’t think that there’s any way the two populations will ever meet up.”

In late July 2025, the 340 surviving snails were released into their native habitat during the wet season, with an irrigation system providing additional moisture and park rangers setting up bait stations and traps to reduce predation from rodents and feral chickens. Each snail was tagged for monitoring purposes.

“I suspect that the snails have spread out beyond the area where we have released them – that’s why it’s really hard to find them,” Foon says. Researchers who have carried out similar projects on other Pacific islands have counselled him. “Sometimes you release the snails and they disappear for a few years with no trace, and all of a sudden [after] a good season of rain … there’s this massive boom in the population,” he said.

Foon tracked snail movements every three days during the first fortnight and continued monitoring for two months, though sightings became increasingly scarce by the end of the year. Rangers now check the site once every three months. Accurate population counts remain challenging at this early stage.

Hyman adds. “We’re know that there’s still snails out there because … we’re still finding babies. So we have high hopes.”

Future Plans for Species Recovery

“Invertebrates are a whole group of animals that are probably underrepresented when it comes to conservation,” Wilson says. “To have these snails front and centre as part of our conservation actions … has been really rewarding.”

The team plans additional reintroductions in 2026. Hyman emphasises that these ongoing efforts are critical for the survival of Advena campbellii and represent a significant milestone in Australia’s conservation history.

We actually are in the process of updating the IUCN listing to show that the Campbell’s keeled glass-snail is not extinct.”

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At Natural World Fund, we are passionate about restoring habitats in the UK to halt the decline in our wildlife.