Biological invaders: the American bullfrog

The American bullfrog (Lithobates catesbeianus) is native to the eastern United States and Canada, but is quickly establishing itself around the world as an invasive species that easily outcompetes many native animals. While amphibians are declining globally from threats such as habitat loss and diseases such as chytridiomycosis (caused by chytrid fungus), the bullfrog continues to expand its range due to its incredible reproductive capabilities (a female bullfrog may produce between 20,000 to 40,000 eggs per year) and its insatiable appetite.

 Bullfrogs are opportunistic predators, and will consume anything that they can fit in their mouths. Mature bullfrogs may weigh over two pounds with a diet consisting of standard fare such as insects, as well as more exotic items including snakes, lizards, turtles, frogs, fish, rodents, bats, and birds. Even the bullfrog tadpoles, which may grow as long as six inches over the course of several years, are known to consume the tadpoles of other frog species.

In the eastern United States there are predators which keep the bullfrog populations in check, but in California there is typically not sufficient pressure and the populations continue to expand. In addition to altering the native food web, bullfrogs are known carriers of chytrid fungus, which does not negatively impact the bullfrogs, but is transmittable to other species of amphibians where it may have detrimental effects (see recent article, “American bullfrogs threaten native wildlife,” published September 13, 2017 at www.plumasnews.com).

 

Bullfrog eating bird Bullfrog eating frog Bullfrog eating fish

 

Bullfrogs in Plumas County

Bullfrogs are highly aquatic, and prefer warm ponds and lakes, although they may inhabit other bodies of water as well. It is likely that the bullfrogs present in Plumas County were accidentally introduced by the food industry, as bullfrog legs have long been used for food. It is also possible that pet bullfrogs were released or escaped, although according to Fish and Game regulations it is illegal to release bullfrogs in California.

In Meadow Valley there are several known populations of bullfrogs present on public lands. These locations include Snake Lake, Smith Lake, and Little Schneider Creek Ponds. Wapaunsie Creek and portions of Spanish Creek are also known to have bullfrogs present, although these are not thought to be breeding sites. It is proposed that bullfrogs within the Meadow Valley area be controlled in order to lessen impacts on native aquatic and terrestrial wildlife.

It is suspected that there may be additional populations of bullfrogs present in ponds on private land within Meadow Valley. Control efforts will be most effective if the location and nature of these populations is known and accounted for, please report any sightings to Mount Hough Ranger District wildlife biologist Colin Dillingham at cdillingham@fs.fed.us. Reporting a sighting does not require any additional action of the part of the landowner, and does not in any way supersede private property rights. If landowners wish to assist in the bullfrog control effort by allowing access to private sites it may be possible to work out a specific agreement to allow non-government volunteers to visit these locations.

What can be done?

The prospect of controlling bullfrogs in Meadow Valley is no small task, but with persistence it may be possible to completely remove bullfrogs from the smaller and more isolated sites, while reducing the population and lessening their impact on sensitive wildlife everywhere else. We recognize the total removal may not be possible, and the project would be reassessed annually to determine progress. This will require teams to work for several hours each month throughout the breeding season, which can last from early April through October. Additional volunteer effort will increase the effectiveness of control and shorten the overall timeline of the project.

We propose to remove bullfrogs under a scientific collecting permit that has not yet been issued by California Department of Fish and Wildlife.  We plan to ask for additional methods of take other than those authorized under a fishing license, including air rifle use with lead-free pellets. The bullfrog legs would be consumed under the permit, so long as no commercial revenue is generated in the process. Stomach contents of the bullfrogs will be analyzed by Plumas Unified School District and Feather River College students as part of a dietary study of the bullfrogs. By allowing local students to participate in field activities and directly contribute to scientific research, this control effort will provide students with valuable hands-on experience at what it takes to manage a complex biological issue.

 Bullfrog eradication has been successful in other areas of California, including along the Merced River in Yosemite National Park, although this required intensive effort. In order to be successful, this project will require multiple years of effort, with the total removal of bullfrogs from the Meadow Valley project area being a ten year goal. Once bullfrogs have been removed from the area it will be necessary to ensure that populations are not re-established from nearby locations.

Community partnerships

A plan to control the bullfrog populations is supported by the USDA Forest Service, Plumas Audubon Society, Feather River College, Plumas Unified School District, the Plumas Corporation, Trout Unlimited, as well as a group of concerned local citizens known as the Meadow Valley Amigos. If you are interested in getting involved in this project, or have concerns about the project that you would like to express, a public meeting will be held on January 9, 2018 at 7:00 PM at the Quincy Public Library.  Please come with any questions, concerns, or suggestions related to the proposed control plan. If you are a Meadow Valley resident and know of any bullfrog locations it is especially encouraged that you consider attending this meeting or submitting a comment to Colin Dillingham, Mt Hough Ranger District Wildlife Biologist at: (530) 283-0555 or cdillingham@fs.fed.us .





https://www.fs.usda.gov/detail/plumas/home/?cid=FSEPRD568023