Chester conservationists have saved a button-sized snail, once thought to be extinct, after successfully breeding and releasing more than 100,000 into the wild.

The greater Bermuda snail was believed to be lost forever until a small surviving population was rediscovered in an alleyway in Bermuda's capital, Hamilton, a decade ago.  

Now, following an international effort, the species has been confirmed as safe and secure - a moment conservation experts describe as "once in a career." 

"It's every conservationist's dream to help save a whole species – and that's exactly what we've done," said Tamas Papp, invertebrates assistant team manager at Chester Zoo.

"This is one of the biggest success stories in conservation.

"This scientific confirmation that we've saved them is testament to the role zoos can play in preventing extinction, and in the power of collaboration, and is something everyone involved will carry in their heart." 

The landmark success has been achieved through a partnership between the government of Bermuda, a conservation researcher from the Canada-based organisation Biolinx Environmental Research and Chester Zoo, where thousands of snails were carefully bred before being returned to Bermuda. 

Six colonies of the released snails have successfully established in Bermuda, an archipelago situated in the north Atlantic Ocean, six hundred miles from the nearest mainland. 

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To boost population numbers, an expert group of scientists and keepers at Chester Zoo were entrusted with several of the snails in hope they could be bred off-site and returned to the wild. 

Gerardo Garcia, animal and plant director at Chester Zoo, was among the team that bred the snails in specially designed pods at the zoo and painstakingly released them in protected woodland habitats. 

He said: "The fact the snails are firmly established in six areas is massive.

"These were not the only sites chosen for the introductions, but they are the ones where the colonies are growing and expanding in range. That itself is really important information, because not much was known about P. bermudensis."

Keepers adapted existing snail husbandry methods to find the best conditions for P. bermudensis to multiply. Their findings are now part of the first conservation breeding guide for the species. 

"They nearly vanished, so being able to say the snails are now safe from extinction is amazing. 

"It's an incredibly good feeling to make a huge difference for a species, and something conservationists might get to say only once in their whole career," added Dr Garcia.  

Snails are among the least researched animals on the planet, and among the most vulnerable to extinction. 

Endemic snails in Bermuda have been affected by habitat loss and climate change, and their decline was accelerated by the introduction of predatory 'wolf snails', and carnivorous flatworms which ate the much smaller native species.

Reintroduction areas were selected and monitored in a process Dr Garcia described as 'like a war game', with expanding populations represented by flags on a map. 

The snails' long-term recovery goes hand-in-hand with nature regeneration projects carried out by the Bermuda government. 

The success of the P. bermudensis project allows the Chester Zoo team to focus its efforts on a second rare species of snail, the lesser Bermuda land snail (Poecilozonites circumfirmatus).   

Ruth Davis OBE, UK Special Representative for Nature, said: "Bringing Greater Bermuda snails back from the brink of extinction is a remarkable achievement.

"This an example of not only brilliant conservation science, but what is possible when we collaborate across borders to restore nature and reverse biodiversity loss."