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Conservation gets complicated when a native U.S. species is appreciated in one part of the country but despised in another. Consider, if you will, the American bullfrog.

“In the Eastern US, where it’s native, its oversized impact is a good thing. In the West, where it’s been introduced, though, the bullfrog tends to wreak havoc.” I recently received those comments from J.J. Apodaca, executive director of Amphibian and Reptile Conservancy. ARC is a nonprofit organization focused on protecting amphibians and reptiles, which includes developing strategies to preserve their habitats.

Our largest frog, the iconic American bullfrog, is a native throughout the eastern United States (except for southern Florida and most of the Okefenokee Swamp) and into southern Canada. It is a mainstay of swamps, rivers, lakes and other wetlands. Bullfrogs will eat almost any animal that doesn’t eat them first. Small snakes, lizards and other frogs, including cannibalism on smaller bullfrogs, have been reported in their diet. The list of documented food items is impressive. I received a photo of one bullfrog sitting on the side of an outdoor pool with a tufted titmouse in its mouth. When I was in high school in New Orleans, someone pitched a baby alligator into the classroom terrarium with our resident bullfrog. The frog promptly ate the gator. People who keep pet bullfrogs often feed them mice.

In the eastern United States, bullfrogs are kept under control by an abundance of native predators, including big watersnakes, alligators, raccoons, hawks and owls. Problems arise when bullfrogs are introduced to regions where they do not have a suite of savvy predators around for population control. Hence in western states bullfrogs have acquired an unfavorable reputation.

In California and Arizona several species of endangered frogs and salamanders, already facing the environmental hazards of habitat loss, have reportedly been eaten by introduced bullfrogs. Although such trends can be difficult to document with certainty, bullfrogs have been implicated in regional declines of native amphibians and fish in other countries where they have been introduced, including Germany, Italy and France. In regions outside their native range, bullfrogs also have the potential for spreading parasites and diseases to local amphibians that have no natural defenses against them, as well as competing with other frogs for food resources.

ARC provides a historical account of how the problem began. In the 1800s in California, “bullfrogs (and their huge hind legs) were initially imported as a food source for the large numbers of miners flooding the state during the Gold Rush.” A few decades later “during the Great Depression, the American Frog Canning Company [located in New Orleans] sold bullfrog breeding pairs and instructions, along with big promises of prosperity, to people all over the country who were desperate to earn a living.” Bullfrog farming turned out not to be a profitable business venture, and the canning company offering a get-rich-quick opportunity is long gone. But the big frogs with their insatiable appetites turned up in lots of places they shouldn’t be, from west Texas to the Pacific Coast.

The introduction of bullfrogs into countries or states outside their native range can lead to ecological disaster. Thanks to ARC, programs are being developed “to curtail the impacts of this powerhouse of a frog in the West through removal, education [programs] and habitat restoration.” Meanwhile, to ensure bullfrogs continue “to thrive in the East, where they belong,” ARC works to protect all native species of amphibians and reptiles, which includes restoring their natural habitats.

The problem of invasive species like bullfrogs is perceived by some as serious enough to warrant controls to limit their introduction into regions where they are not native. The need to institute legal roadblocks to limit free transport, sale or even ownership of a wild species is unfortunate. But even more unfortunate are the consequences of the introduction of a species in places where it does not belong.

Bullfrogs are the largest frogs in North America. Native to the eastern states, they can be an unwelcome invasive species in the West. Photo courtesy Parker W. Gibbons