Are frogs being eaten to extinction? We're used to hearing about how disease, climate change, and habitat degradation are endangering amphibians, but conservationists are warning that frogs could be going the same way as the cod. Gastronomic demand, they report, is depleting regional populations to the point of no return.
David Bickford of the National University of Singapore and colleagues have called for more regulation and monitoring in the global frog meat market in order to avoid species being "eaten to extinction".
Statistics on imports and exports of frog legs are sparse as few countries keep track of the amount of meat harvested and consumed domestically.
According to UN figures, global trade has increased in the past 20 years. France - not surprisingly - and the US are the two largest importers; with France importing between 2500 and 4000 tonnes of frog meat each year since 1995.
But although frog legs are often thought of in the West as a quintessentially French dish, they are also very popular in Asia.
Bickford estimates that between 180 million to over a billion frogs are harvested each year. "That is based on both sound data and an estimate of local consumption for just Indonesia and China," he says. "The actual number I suspect is quite a bit larger and my 180 million bare minimum is almost laughably conservative."
Even top French chefs may be unaware of where their frogs are coming from. Bruno Stril, teaching chef at the Cordon Bleu school in Paris, France, is unsure where his suppliers source their frog legs. "I would like for them to come from France," he says. But he expects that most of the meat comes from other countries.
Stril is on the right track. Indonesia is the world's largest exporter of frog meat, exporting more than 5000 tonnes of frog meat each year, mostly to France, Belgium and Luxemburg.
Bickford and colleagues say European kitchens initially found their own supplies in the surrounding countryside, but the fact that they are now importing from Asia suggests local populations were over-harvested. This, they say, could be a sign that frog populations, like many fish populations, will be harvested to near extinction.
"Overexploitation in the seas has caused a chain reaction of fisheries collapses around the world," the researchers write. "This experience should motivate better management of other exploited wild populations."
James Collins, of the World Conservation Union, says the Californian red-legged frog offers some evidence for the theory. This species was first harvested for food in the 19th-century California gold rush and eventually the population began to crash.
However, Collins cautions that "at the moment we have no data indicating that commercial exploitation has led to the extinction of any amphibian species." He says the Bickford team's evidence is worrisome, but inconclusive.
Most harvested frogs are skinned, butchered and frozen before being shipped overseas. This makes it difficult to know exactly what species are being killed. Indonesia is thought to mostly export crab-eating frogs, giant Jana frogs, and American bullfrogs. How much meat is consumed within Indonesia's borders is also something of a mystery. Some studies suggest it could be between two and seven times what is exported.
"There are a heck of a lot of frogs being eaten," says Bickford. "Much more than most people have a clue about."