The largest amphibian in the world – the two-metre-long Chinese giant salamander (Andrias davidianus) – is not one species but five, and all of them are going extinct.
That’s the sad news from two linked studies published in the journal Current Biology, which find that a deadly combination of habitat destruction, poaching and, ironically, attempts to restock using captive-bred animals has seemingly doomed the creatures.
Chinese giant salamanders – native, of course, to some parts of China – have historically been regarded as a high-value food source and formed part of some regional cuisines.
Several years ago, recognising that populations were under considerable stress, the Chinese authorities banned wild capture and encouraged captive breeding programs – an approach endorsed by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which recommends high level protection.
Most of these programs have been in the form of commercial farming. Wild-captured foundation salamanders cannot be traded, but second-generation farmed salamanders are sold for food, often fetching as much as $1500 per animal. The high price tag represents a strong incentive to poachers.
Some farmers produce surplus animals that are released into the wild in an effort to boost the natural population, but this approach, reports a team led by Fang Yan of the Sprott Centre for Stem Cell Research in Ottawa, Canada, has resulted in multiple problems.
Using mitochondrial DNA analysis, the researchers established that the giant salamander comprises five distinct (although outwardly almost identical) species. Although research as far back as 1998 established at least two species, there has been no attempt to discern the optimum conditions each needs, or adjust the taxonomy.
As a result, Yan’s team finds, trade between farms has resulted in the salamander genome becoming homogenised, with a species native to northern China now accounting for most captive-bred stocks.
“Today, millions of Chinese giant salamanders live in farms and their progeny have been released into local rivers as part of government-promoted conservation action, but without pre-release assessments such as genetic testing or screening for disease,” the researchers write.
This re-wilding strategy, say a second team headed by Samuel Turvey of the Chinese Academy of Sciences, will likely spread pathogens and further dilute the lineages of the various species. Beyond that, he and his colleagues discovered, the hope of boosting native populations may well be forlorn – on the grounds that most have already disappeared.
Over four years, the scientists set traps for giant salamanders in waterways in 97 counties, using historical records and habitat modelling as clues. All up, only four locations were found to contain the animals, and only 24 specimens were found.
Turvey and his colleagues followed up by questioning villagers near all of the sites regarding the salamanders. More than 85% of the people interviewed recognised a picture of one, but when asked how long had passed since they had last seen one, the average estimate was 19 years.
Turvey and colleagues conclude with a call for targeted, non-commercial captive breeding programs for each of the five newly revealed salamander species, saying such an approach is “probably essential” if the amphibians are to survive.