This is a tragic story of a troop of little snails that live on islands in the South Pacific, or at least they used to.
Partula snails were the victims of a botched attempt at biological control; giant snails were brought to the islands for people to eat, but instead the snail ended up demolishing local gardens and crops; another snail species (a predator) was then brought in to eat the big snails, but instead they began to munch the local Partula snails.
Of at least a hundred Partula species, a third went extinct and 11 or 12 other species were whisked away into captivity in the 1990s and kept from the brink of extinction in zoos around the world.
This cautionary snail tale contains a message of hope. Zoo-bred snails are being taken back to their native home in the Pacific.
Listen to the programme on BBC website and download a podcast.
Picture: Reintroduced Partula dispersing on Moorea in French Polynesia. ZSL