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The largest amphibians in the world are on the very brink of extinction. Not only have wild populations of Chinese giant salamanders been decimated, it turns out there are five species rather than one, each with a truly minuscule population.

Chinese giant salamanders () can grow up to 1.8 metres long. They spend all their lives in mountain streams in their native China.

Researchers searched for wild salamanders between 2013 and 2016 in 16 of China鈥檚 23 provinces. It was one of the largest wildlife surveys ever conducted in China.

They found just 24 giant salamanders. 鈥淲e only found them at four of the 97 sites we visited,鈥� says of the Zoological Society of London, UK. 鈥淭he speed at which populations have collapsed is terrifying.鈥�

30 years ago, . Their since is most likely due to a 鈥渞e-branding鈥� of the salamanders as delicacies, beginning 15 years ago. People began farming them for their meat. Poachers caught wild salamanders to sell to farmers, removing them from the wild.

And the news only gets worse.

Five species not one

A team led by of the Kunming Institute of Zoology in China compared DNA collected over the past 10 years from 70 wild-caught and 1034 farm-bred salamanders. The genetic analysis revealed that what was thought to be a single species is at least five, possibly eight.

The species diverged from a common ancestor over 4 million years ago, and since then have been geographically and genetically isolated. Each colonised a separate river system, including those of the Pearl, Yangtze and Yellow Rivers.

This means that each species has a tiny population. What鈥檚 more, a well-intentioned attempt to boost the number of wild salamanders has backfired spectacularly.

A government-supported programme encouraged farmers to release some of their farmed salamanders into the wild. Since 2008, farmers have released at least 72,000 salamanders.

But since nobody realised there was more than one species, the salamanders were released indiscriminately. As a result the species have all started interbreeding, mixing up their genes, so some of the species may already be extinct.

When Che鈥檚 team analysed mitochondrial DNA from salamanders caught recently in the Pearl and Yangtze river systems, they found that all of them were Yellow River salamanders.

There is now only one way to save the wild populations, says Turvey. We must use genetic screening tests to identify any as-yet-unhybridised salamanders living on farms. Then each surviving species can be bred in isolated breeding colonies.