These tiny snails were once feared extinct. Now, scientists say, ‘they’re doing absolutely brilliantly’

A decade ago, the only known surviving population of greater Bermuda land snails were discovered in an alleyway in the capital city of Hamilton, where they’d made a home on concrete slabs in the moisture created by a dripping air conditioner. 

Now the native creatures appear to be thriving in the wild once again. 

That’s thanks to the work of conservationists who bred them in captivity and released more than 10,000 into the archipelago’s protected wooded habitats over the last seven years.

“They’re doing absolutely brilliantly,” Katie Kelton, who helps breed and care for the snails at U.K.’s Chester Zoo, told As It Happens host Nil Köksal.  

“We’ve had confirmed breeding … and the numbers are starting to build now, so really we can say that this project has been a success.”

The decade-long effort to save the species from the brink of extinction is a joint effort by the Chester Zoo, Canada-based Biolinx Environmental Research, and the government of Bermuda. A study documenting the program’s success will be published in the upcoming edition of Oryx, The International Journal of Conservation.

But the battle isn’t over yet. The snails still face threats from habitat loss and invasive predator species — the very things that nearly wiped them off the face of the planet. 

Important to ecosystems, and ‘really cute’

Greater Bermuda land snails, or P. bermudensis, are only the size of a button or a quarter, but they play an outsized role in the ecosystems of Bermuda, the only place in the world where they are found. 

They act as decomposers, breaking down leaf litter on the ground and returning the nutrients to the soil. Their shells are also a source of calcium for their natural predators, like native birds and reptiles, who, in turn, use that calcium to lay strong eggs.

Plus, Kelton says, “they’re really cute and pretty.”

“They’ve got all this beautiful patterning on them,” Kelton, an invertebrate keeper at Chester Zoo, said.  “Honestly, I’m a bit obsessed with them.”

The International Union for Conservation of Nature (IUCN) lists P. bermudensis as critically endangered.

They’d been driven to the brink of extinction by human incursion into their habitat, and with it, the introduction of invasive predatory species, including rats, feral domestic chickens, flatworms that travel in potted plants, and several species of snails, including one that was brought to the island to kill off a different invasive snail that was threatening crops.

The IUCN hailed their successful re-introduction last week during its Reverse The Red Day, which celebrates efforts to reduce biodiversity loss.

“We are excited to celebrate this win,” Michael Clifford, Reverse the Red’s strategy director, said in a statement.

It was no easy feat, says Kelton. When the captive-breeding team first got the snails, they knew very little about them. They had to make several tweaks to their diet, temperature and environment before they figured out the perfect conditions for breeding.

“We’re a team of people that are obsessed with snails, we’re obsessed with invertebrates, and we’re just really passionate about conservation,” she said. “It has definitely been a labour of love.”

Back in the woods, but not out of the wood

Timothy Pearce, curator of mollusks at Carnegie Museum of Natural History in Pittsburgh, says having research like this is key for developing protocols for other captive-breeding and re-wilding programs, including one he’s working on with local snails.

While he says he’s heartened that the team has successfully re-introduced the snails to the wild, he cautioned that their long-term survival is not guaranteed.

“I am glad to hear the reintroduced native snails are in secure areas, but how long will they remain secure?” said Pearce, who was not involved in the Bermuda snail research.

“I look forward to learning whether they can keep the predators away so it will be a permanent solution.”

In fact, not all the newly re-wilded snails fared well. 

Over the last seven years, scientists slowly released them in 27 different sites across the archipelago. Those on main island sites failed to get a foothold, likely because there were more people, and more predators. 

But reintroductions to six offshore islands have been a success, with the snails breeding several generations, expanding their territory, and integrating themselves back into the local ecosystems.

They’re doing especially well at their first re-introduction site, Nonsuch Island, a 16-acre nature reserve that Bermuda senior biodiversity officer Mark Outerbridge calls “a living museum of pre-colonial Bermuda.”

“Nonsuch is home to many of our rarest and most endangered flora and fauna and is the subject of regular conservation management,” Outerbridge said in an email. “Public access is limited to minimize human impacts and non-native species are continuously controlled.”

Bermuda administers birth control to some invasive predators, Outerbridge said. For others, they have launched awareness campaigns to educate landowners about how to avoid accidentally introducing non-native species to the areas where the snails have taken up residence.

“It is going to require constant diligence to keep the reintroduced colonies safe,” he said.

Kelton, meanwhile, says she’s honoured to have played a part in saving the snails she’s come to love.

“A lot of people do not care about snails and really overlook them,” she said. “But we really just wanted to make sure that we could give this species a chance.”