A disease-carrying bullfrog straddles a cultural divide

Miles Young strode down a narrow passageway in a bustling Chinatown fish market, methodically scanning aquariums and plastic bins filled with hundreds of live frogs selling for $3.99 a pound.

They were imported from frog farms in Taiwan, the environmental activist and former game warden said.

The species is particularly susceptible to a skin fungus linked to vanishing amphibians around the world. And the conditions in which bullfrogs are raised, transported and sold are ideal breeding grounds for the fungus and its waterborne zoospores.


“It should be against the law to bring diseased nonnative animals into California,” he grumbled. “But every time someone proposes a ban on bullfrogs, politics gets in the way and nothing gets done.”

Batrachochytrium dendrobatidis is a chytrid fungus that was first identified in 1998 and is thought to have originated in Japan. It causes a thickening of the skin, which impairs gas exchange and the animal’s ability to absorb water, triggering rapid mass die-offs of frog populations.

Bullfrogs carry the fungus but do not die from it. Most of the millions of bullfrogs imported to California each year for use in the food, pet and dissection trades are infected with the fungus, according to several recent studies.

The disease can spread to native frog populations if an infected frog escapes captivity or is set free, or if the water from its holding tank is released into the environment.

Yet, proposals to ban the importation of bullfrogs have cultural implications, which have pitted environmental organizations against Asian Americans who regard the animals as traditional cuisine and important commodities for family-owned businesses. A similar rift opened recently over banning the sale of shark fins.

“So long as nonnative frogs are brought into the state, it is inevitable that some will escape or be set free,” said biologist Kerry Kriger, executive director of the nonprofit group Save the Frogs! “It is also inevitable that the infectious diseases these animals carry will enter California ecosystems.”

The state Fish and Game Commission, which sets policy for the Department of Fish and Game, voted to ban permits authorizing importation of frogs and turtles. The department has chosen not to implement the ban.

The squabble started in March 2010, when the commission voted unanimously to direct the department to stop issuing permits for the importation of live frogs and turtles for food. A month later, however, it held a “reconsideration hearing” at the request of Asian American leaders who included five Assembly Democrats and state Sen. Leland Yee (D-San Francisco), who called the ban an assault on their cultural heritage.

Opponents also said it unfairly targeted Asian American businesses because it did not affect the sale of turtles and frogs at pet stores.

In testimony before the panel, Yee, an unsuccessful candidate in the Nov. 8 San Francisco mayoral election, said, “For over 5,000 years, it has been the practice of both the Chinese community and the Asian American community to consume these particular animals. They are part of our staple. They are part of our culture. They are part of our heritage.”

Kriger, however, testified that the vast majority of frogs being imported for food are American bullfrogs, which have only a relatively recent history in Asian cuisine. Native to eastern North America, the bullfrogs were introduced to California in the late 1800s to provide food for gold miners who had eaten native red-legged frogs to near extinction. Later, bullfrog farms in China, Taiwan and Brazil began supplying live amphibians to Asian markets around the world.

Despite pleas, the Fish and Game Commission decided not to rescind its decision. But the department opted to continue issuing permits to import frogs and turtles. Stopping the importation of frogs and turtles for food was “a low priority for the use of the department’s very limited resources,” Department of Fish and Game Director John McCamman wrote in a memorandum to the commission earlier this year.

“This is about a cultural practice, and the department doesn’t like getting in the middle of those things,” commission executive director Sonke Mastrup acknowledged in an interview. “We may revisit it again. But we would have to find the political will to bite the bullet and actually change the law.”

The battle over the bullfrog is far from over. In October, Save the Frogs! launched a petition calling on Gov. Jerry Brown to ban the importation, sale, release and possession of American bullfrogs in California.

Separately, the U.S. Fish and Wildlife Service is studying a proposal by Defenders of Wildlife to ban the importation of live frogs unless they are accompanied by a health certificate verifying that they are free of the chytrid fungus.

“It’s a very complex subject,” said Susan Jewell, a spokeswoman for the agency’s aquatic invasive species branch. “We’re still working on what our recommendation will be.”

Then there is Santa Cruz County, home to dwindling populations of threatened California tiger salamanders and California red-legged frogs. Later this year, it expects to become the first county in the nation to ban American bullfrogs.

Today, eradication of the bullfrog, known to scientists as Rana catesbeiana, is a costly and time-consuming priority of management plans for many of California’s threatened amphibians.

When it comes to ecological destruction, few invasive species can match the havoc wrought by the American bullfrog’s voracious appetite for anything that can fit in its big mouth, including ducks, bats, snakes and other amphibians.

In a county already swarming with bullfrogs, “our main goal is set an example for other cities and counties and help expand awareness about the problem and the importance of native amphibian conservation,” said Santa Cruz County Fish and Game Commissioner Chris Berry.

The proposal has the support of Defenders of Wildlife, the Humane Society of the United States, Action for Animals and the Elkhorn Slough National Estuarine Research Reserve in neighboring Monterey County.

“We have about 1,200 California red-legged frogs, which is one of the largest populations for miles around,” said Nina D’Amore, the reserve’s resident amphibian biologist. “About 30% of them are infected with the fungus.”

On a recent weekday, she spent an hour waist-deep in water, peering into tules and willows, seeing only red-legged frogs and chorus frogs on the mossy banks of a one-acre pond rendered nearly free of bullfrogs after years of eradication campaigns.

“An interesting thing happened after we took out the bullfrogs,” she said with a smile. “We started seeing a lot more red-legged frogs.”

But a few minutes later, she noticed a tell-tale shape on shore: an olive green frog with a spotted back and a tinge of yellow on its chin. The frog leaped into the water, disappearing in the muddy bottom. Her face fell.

“It’s not easy getting rid of bullfrogs,” she said.