Conservationists have reintroduced hundreds of tiny snails on a rocky Atlantic island after a zoo breeding programme pulled four species back from the brink of extinction. The molluscs have been returned to Bugio island on the Madeiran archipelago, helping to restore habitat and support biodiversity on land once grazed bare by feral goats, mice and rabbits.
Rescue mission
Experts at Chester Zoo and ZooParc de Beauval in France were asked to step in by the Madeira government when a handful of snails - from the last known wild population - were carefully transported to each zoo in an effort to save them from extinction. Among them were 21 Geomitra coronula, believed to the last of their kind, which were found clinging to life beneath a single rock.
More than 300 of their descendants bred at Chester Zoo have returned to the wild, alongside 270 specimens of Discula lyelliana bred by specialists in France.
Threats to survival
Tamas Papp, assistant team manager for invertebrates at Chester Zoo, said: "It had to be a rapid rescue mission for all four species of snail. Over the course of a few hundred years, people managed to destroy the islands’ woodland and introduced rabbits and goats, which prevented native plants from regrowing. Worse still, they accidentally brought mice with them. With no natural sources of drinking water on the islands, the mice quickly turned to the snails, whose bodies are made up of around 80% water, using them as a vital source of hydration. As a result, snail populations were wiped out."
"By the time the Madeira government contacted us for help, one of the species, Geomitra coronula, was so close to extinction that its entire global population could fit inside a single petri dish. We knew we had one shot to save them. If we missed this chance, that was it - they were gone."
Preparation and release
Madeiran Government conservationists prepared for the snail release by removing the invasive species and restoring the island to pristine condition. These measures were also designed to protect at-risk sea birds.
Dinarte Teixeira, IFCN conservation biologist and project manager, said: "The Desertas islands are the only place in the world where these precious snails can be found. For 100 years we thought they’d gone forever, but thanks to this team effort, these reintroductions are proving successful. We will keep monitoring the snails as they settle back into the wild."
Night-time operation
The team had to travel at night, using red spectrum torches to find snail-friendly cracks in the rock, as the islands’ rare sea birds are sensitive to artificial white light. Chester Zoo experts are now looking after all four species, Atlantica calathoides, Geomitra grabhami, G. coronula and Discula lyelliana in on-site breeding pods built to mimic their natural environment.
Nothing was known about their care, so specialists quickly established what the rescued snails would eat, which temperatures suited them best and about their breeding cycles. Anaëlle Loiseau, species manager at ZooParc de Beauval, said: "The snails have regular veterinary tests to verify that it’s safe for them to be released into the wild. Before the reintroduction, we choose individuals that are of age to breed - or close to - from various generations to offer diversity in the individuals released."
"These reintroductions are important milestones in this conservation programme. They prove that the work carried out by zoos is vitally important in securing a future for wildlife on our planet."
The released snails measure no bigger than 8mm in size, but they are important to the health of ecosystems as they eat vegetation and enrich the soil. Conservationists believe their recovery will support the broader restoration of fragile island habitats.
