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Once feared extinct, a tiny snail has been rediscovered at Southlands

Lazarus snail: Vertigo bermudensis, an endemic species of micro-snail, was found by a visiting Czech Republic specialist during a search funded by the Bermuda Zoological Society (Photograph by Jeff Nekola)

A species of tiny snail feared to be extinct has been rediscovered at Southlands.

In the Spring edition of the EnviroTalk Newsletter, published by the Department of Environment and Natural Resources, Robbie Smith, curator of the National History Museum, said a thriving population of Vertigo bermudensis – an endemic species of micro-snail – was found under leaf litter beneath the park’s banyan trees.

“Preliminary molecular genetic analyses confirmed that V bermudensis is a long isolated endemic sister species to Vertigo milium of the southeastern US coastal region,” Dr Smith said.

“The discovery of this population provides some hope that other living populations, and perhaps the other ‘missing’ species, exist elsewhere.”

Dr Smith said that Bermuda was known to have four endemic species of micro-snail, which measure less than 2.5mm – about the same size as the snout of the hog on the Bermuda penny.

Of those species, two – Vertigo bermudensis and Vertigo marki – were feared to be extinct.

“This aspect of our island’s biodiversity had not been thoroughly surveyed in almost a century,” Dr Smith said.

“With a grant of the Bermuda Zoological Society, Jeff Nekola of Masaryk University in the Czech Republic visited the island for almost two weeks in January to search for them. Mark Outerbridge and I guided Jeff around and assisted with the sampling.

“Dr Nekola has a deep experience studying these types of snails across North America and brought with him critical sampling tools: a set of sieves, designed to separate the very tiny snails from soil and leaf litter.”

Dr Smith said they visited Paynter’s Vale, the Walsingham Nature Preserve and Church Cave, where recently-dead shells of micro-snails were reported.

“Initial sampling efforts in Walsingham and Admiral’s Cave produced nothing,” he said.

“Church Cave and Paynter’s Vale contained other dead endemic micro-snail shells, but none of which had been alive within the last 20 years.”

Dr Smith said Dr Nekola deduced that the changing nature of Bermuda’s woodlands – specifically the loss of Bermuda cedars and their replacement by invasive species – had contributed to the loss of micro-snails on the island.

He said it was a “great surprise” to find healthy Vertigo bermudensis near the entrance to Southlands, while dead shells were found in leaf litter at Spittal Pond and under a surviving cedar at Walsingham.

“This nearly invisible part of Bermuda’s unique biodiversity deserves attention and protection and we are indebted to Jeff for his effort and expertise,” Dr Smith added.

The newsletter also highlighted efforts to restore the island’s population of greater and lesser Bermuda land snails.

The greater Bermuda land snail was considered extinct for 30 years, until a colony was located in 2014.

No living lesser Bermuda land snails have been found in the wild since 2004, but recently dead specimens have been recovered, suggesting that some “cryptic colonies” may survive.

Both species have been reared in captivity at the Chester Zoo in the UK in an effort to protect against extinction, and efforts have since been launched to reintroduce the species.

EnviroTalk said that more than 100,000 greater Bermuda land snails have been released at 27 locations including small, woodland island nature reserves where predators are “absent or controlled”.

Meanwhile, since 2020, nearly 9,000 lesser Bermuda land snails have been released at four locations deemed suitable for their long-term survival.

The work has given mixed results, with the population of greater Bermuda land snails on the rise at one location on Nonsuch Island while the species has failed to establish itself at other sites on the island.

“Additional surveys have shown that these snails inhabit both native and invasive-dominated woodlands and aggregate around limestone features such as overhangs and damp crevices,” the newsletter said.

“So far we have been unable to confirm the success of introductions to the main island sites, where predators and habitat disturbance are extensive, but the releases were relatively recent.

“It is still too early to tell whether the releases of the lesser Bermuda land snails have been successful, but we remain cautiously optimistic as some individuals have been detected one year after introduction at an intensively monitored site.”

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Published March 21, 2023 at 12:12 pm (Updated March 21, 2023 at 12:35 pm)

Once feared extinct, a tiny snail has been rediscovered at Southlands

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