American Bullfrog Invasion and Impacts on Native Species in the Pacific Northwest

American bullfrogs are native to eastern North America but have been widely introduced around the world. They are frequently linked to population declines of native species, including smaller native amphibians. These large frogs compete with smaller species for food and space. They can also spread disease in areas where they have invaded. Bullfrogs are usually introduced into new habitats through human activities like the pet trade or bait for recreational fishing. After introduction, bullfrogs are capable of thriving and quickly reproducing in a wide range of habitats. To help control the spread of invasive bullfrogs and protect local food webs, land and resource managers need information on when and where bullfrogs are invading and interacting with native species.

In the western United States, bullfrogs have the potential to slow recovery of the Oregon spotted frog, a Threatened species under the Endangered Species Act. Oregon spotted frogs are susceptible to competition and predation by bullfrogs. Bullfrogs are much bigger than Oregon spotted frogs and tend to live in the same habitats. We are involved in several studies aimed at learning more about bullfrog invasion dynamics and whether bullfrog removal at sites where the two species co-occur could benefit Oregon spotted frogs.

Explore the science pages in the tab above to learn more about American bullfrog research at FRESC.