Santa Cruz County in California could soon become the first county in the U.S. to ban the import, sale and possession of American bullfrogs (Rana catesbeiana). Last week, Santa Cruz County Board of Supervisors Chairman Mark W. Stone sent a letter to the board urging it to enact a ban in 2012. Stone's request followed a similar letter to the supervisors from the chair of the county's Fish and Game Advisory Commission.

Bullfrogs pose several threats to the native amphibians of California, many of which are endangered. When bullfrogs—the largest frogs in North America—escape or are released into the wild, they have a tendency to eat other amphibians and any other wildlife that will fit in their mouths. Their size also allows them to outcompete native species for food. Even worse, a large portion of the bullfrogs imported into this country—62 percent according to one study—are infected with the deadly chytrid fungus (Batrachochytrium dendrobatidis), a lethal skin disease which has already been blamed for extinctions of about 100 amphibian species around the globe. Bullfrogs themselves are relatively resistant to the chytrid fungus, but that doesn't stop them from spreading it to other species in the wild.

Bullfrogs are native to the eastern U.S., although the millions imported into California every year come mostly from China, Vietnam, Taiwan and Mexico, where they are farmed for sale as food or pets as well as for dissection in schools. (See my previous story, "How Eating Frogs Legs Is Causing Frog Extinctions.") According to the Global Invasive Species Database, American bullfrogs have been introduced in more than 40 countries on four continents and are "responsible for outbreaks of the chytrid fungus found to be responsible for declining amphibian populations in Central America and elsewhere." The database is published by the Species Survival Commission of the International Union for Conservation of Nature.

In his letter, Fish and Game Advisory Commission chair Russel Maridon acknowledged that it is unusual for a county rather than a state to attempt such a ban, but it is necessary because of inaction at the state level. "We recognize that it is more appropriate for this regulatory action to occur on the state level," the letter read. "While the State of California Fish and Game Commission has twice voted ban the importation and sale of bullfrogs, the Department of Fish and Game still allows it." (The state commission, in theory, sets policy for the state department, but the department does not have to follow all of the commission's decisions.) "Therefore—in addition to initiating development of language to ban bullfrog importation and sales in the County—we also encourage the [Board of Supervisors] to contact California Secretary of Natural Resources John Laird to communicate its concerns about this matter and ask that he review the state commission's relative inaction on this matter."

The initial request to ban bullfrogs came from the nonprofit Save the Frogs, which is based in Santa Cruz and has actively pushed to regulate the species in the state. "This type of legislation is already in effect for other known, injurious, invasive species in California," says Kerry Kriger, founder and executive director of Save the Frogs, who notes it would just take adding the American bullfrog to the existing list of amphibians banned in California to end all imports and sales. "We're hoping to set a precedent in this county and use it to educate politicians and raise awareness throughout the state."

Endangered amphibians present in Santa Cruz County include the Santa Cruz long-toed salamander (Ambystoma macrodactylum croceum), California tiger salamander (Ambystoma californiense) and California red-legged frog (Rana draytonii). Bodies of all three species—along with the endangered giant garter snake (Thamnophis gigas)—have been found in the stomachs of American bullfrogs in the county.

Photo: American bullfrog by Carl D. Howe via Wikipedia. Used under Creative Commons license