An endangered species of snail saved from extinction by a breeding programme has been released into the wild.

More than 11,000 greater Bermuda land snails, bred at a British zoo, have been given a new home on Morgan’s Island, which is owned by the Bermuda National Trust.

A spokesman for the BNT said the endemic Poecilozonites bermudensis snails, once plentiful, had been almost wiped out in the late 1970s by introduced predators, pesticides and human expansion.

Conservationists presumed the invertebrates were lost until Alex Lines, a Bermuda Aquarium, Museum and Zoo intern, found small populations clinging to life in isolated spots.

He had been sent out to search for the creatures during the summer of 2000, in the wake of a December 1999 story in The Royal Gazette.

In 2014, the snail species again showed its resilience, when a cluster of them was discovered in a Hamilton alleyway by Mr Lines’s father, Bruce.

Specimens were sent to London Zoo for a captive breeding programme and Chester Zoo joined in the effort.

The first repatriation of snails to Bermuda was made in February.

Nonsuch Island took 4,000 of the creatures and the BNT’s island in Ely’s Harbour, Sandys, received its first batch last month.

Mark Outerbridge, the wildlife ecologist for the Department of Environment and Natural Resources, said Morgan’s Island had been chosen as a haven because it was “not threatened with future development”.

The island’s palmetto forest offers the snails a good habitat and its cover of poison ivy deters visitors from walking on the animals.

A team of Trust members freed the snails on July 17 with Dr Outerbridge and Alison Copeland from the department, as well as Amber Flewitt from Chester Zoo.

Gerardo Garcia, the curator of lower vertebrates and invertebrates at Chester Zoo, said the snail was “one of Bermuda’s oldest endemic animal inhabitants”.

Dr Garcia added: “It has survived radical changes to the landscape and ecology on the remote oceanic islands of Bermuda for up to a million years, but, since the 1950s and 1960s, it has declined rapidly.

“Its demise is mainly due to changes to their habitat and the introduction of several predatory snails.”

Carnivorous snails imported to control accidentally introduced milk snails and flatworms took a heavy toll on the Bermuda land snails, which are particularly vulnerable because for thousands of years before 1503, they had no natural predators.

Nonsuch Island’s fauna and flora are culled from imported species and Morgan’s Island does not appear to be home to any of the predators.

Dr Outerbridge said: “I am profoundly grateful to the Bermuda National Trust for allowing us to introduce these unique snails to Morgan’s Island.”

He added: “The creation of such island refuges is extremely important to the long-term survival of this species.”

Bermuda’s land snails were the basis of research by the late Stephen Jay Gould, a prominent Harvard University paleontologist, who, as a graduate student, completed his doctorate on them.

Their fossils were one of many influences on his controversial evolutionary theory, punctuated equilibrium.

Dr Gould, who died in 2002, also provided a record of the near extinction of the greater Bermuda land snail species, after he had earlier found thousands of live snails when he visited Bermuda in the 1960s.

He wrote that he could find none after a 1973 visit.

Dr Outerbridge said the public would be unlikely to find the Poecilozonites variety of snails on the mainland.

He said that if any were discovered, the Department of Environment and Natural Resources would accept specimens to add to the breeding programme to boost the genetic diversity of its stock.