Frog legs are still an amazingly popular food item around the world, including here in the U.S. According to a new report, an average of 2,280 metric tons of frog legs are imported into this country each year—that's the equivalent of somewhere between 450 million and 1.1 billion frogs. Another 2,216 metric tons of live frogs are imported every year for sale in Asian-American markets.

The demand for frogs is even greater in the European Union, which imports an annual average of 4,600 metric tons of frog legs, mostly to Belgium (53 percent), France (23 percent) and the Netherlands (17 percent).

These numbers come from a new report, "Canapés to Extinction: The International Trade in Frogs' Legs and Its Ecological Impact" (pdf), released July 26 by the wildlife conservation groups Pro Wildlife, Defenders of Wildlife and the Animal Welfare Institute.

This enormous appetite, totaling billions of frogs every year, is contributing to frog extinctions around the world in two manners: First, too many frogs are collected from the wild, in some cases nearly depleting natural populations; and second, the rampant international trade in frog legs and live frogs is the major reason for the spread of the deadly chytrid fungus (Batrachochytrium dendrobatidis), which has already been blamed for around 100 amphibian extinctions around the globe.

The supply of frogs used to be dominated by sales from India and Bangladesh, but those countries overharvested their frogs back in the 1980s. The vast majority of wild frogs imported into the E.U. and U.S. today come from Indonesia. Frogs are also farmed in China, Vietnam and Taiwan for the export market. Mexico is also a major supplier of live frogs to the U.S.

Interestingly, a large number of farmed frogs imported into the U.S. from Asia were actually originally a native species, the American bullfrog (Rana catesbeiana, or Lithobates catesbeianus), North America's largest frog species. According to Save the Frogs (an organization which is not affiliated with this report), "A recent study estimated that 62 percent of the bullfrogs entering California from Asian frog farms are infected with the chytrid fungus. Bullfrogs serve as perfect vectors for fungus, as the frogs can survive infection loads of millions of chytrid zoospores. Because the infected frogs don't die from the fungus, they are able to spread the pathogen to native amphibian populations." A study published in 2004 in The Herpotological Journal (Vol. 14, pp. 201-207; not available online) found that bullfrogs showed remarkable resistance to the chytrid fungus and rarely, if ever, die from exposure to it. Most amphibian species have an 80 percent mortality rate when chytrid arrives in their habitats.

Other popular species in the frog trade tend to also be on the large side, such as the Asian brackish (or crab-eating) frog (Fejervarya cancrivora) and Javan giant frog (Limnonectes macrodon). About 20 total species comprise the bulk of the international trade, according to the report. Another 180 species are consumed in their countries of origin. Exact statistics on which species are being imported and eaten are incomplete, because most imports are already skinned, processed and frozen, making them hard to identify.

The three organizations behind this report are now calling for increased regulation of the frog trade under the Convention on Trade in Endangered Species of Wild Fauna and Flora (CITES). That agency has the authority to restrict some hunting and harvesting, create humane standards for frog handling and killing, set monitoring criteria for wild populations, and require that all imported meat be frozen, which would slow the spread of disease.

Last year, the U.S. Fish and Wildlife Service asked for public comments on a proposal to ban the import of live frogs under the Lacey Act, which regulates the import or transport of wildlife species that are either dangerous to humans or the environment. The public comment period ended in December; there is no word yet on if the proposal will become law.

Photo by Graham Holliday via Flickr, used under Creative Commons license