They were down to 21 tiny survivors, all clinging to a rock on a remote Atlantic island.
Experts from Chester Zoo have returned the Madeiran land snails to Bugio Island, part of Portugal’s Madeira archipelago, after they were believed to be the last of their kind.
The Madeira government asked Chester Zoo experts to help with the conservation effort.
The conservationists had to scramble from the water up a cliff face in the dark to find cracks in the rocks where the snails could be safely left.
Tamas Papp, assistant team manager for invertebrates at Chester Zoo, said: “We knew we had one shot to save them. “If we missed this chance, that was it: they were gone.”
He added: “It might be the trickiest reintroduction we’ve ever done. “We had a short window due to rough weather, and there’s no jetty on the island. “We had to jump straight into the water, climb out, put helmets and harnesses on, and start scrambling up the cliff face.”
The snails measure no bigger than 8 millimetres and are important because they eat vegetation and enrich the soil.
They will be monitored as they settle back into the wild.
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