Protecting Washington’s wetlands from invasive bullfrogs
Washington’s mountain ranges, rivers, and marine waters get a lot of love, but our wetlands are pretty incredible places too. Although they might not look like much at first glance, wetlands are biodiversity hotspots, providing habitat for a staggering array of life, from aquatic invertebrates to amphibians, fish, reptiles, mammals and birds. When they’re healthy, wetlands help filter our water, mitigate flooding, and store carbon.
The health of these wetlands is a delicate balancing act, and in wetlands across Washington, that balance is being disrupted by a hungry and prolific invader from the east: the American bullfrog.
The largest frog in North America, American bullfrogs (Rana [Lithobates] catesbeiana) can grow to be over a foot long and weigh well over a pound. Bullfrogs are generally considered native east of the Rocky Mountains, but considered invasive in the Pacific Northwest. In Washington, they are classified as an aquatic invasive species, reducing biodiversity and negatively impacting the balance of our native ecosystems.
Bullfrogs are very adaptable and can quickly establish and overtake wetlands. Bullfrogs are voracious, opportunistic predators that eat practically anything they can fit into their mouths, from native frogs and small fish to small birds, snakes, and even turtle hatchlings and other bullfrogs. They’re capable of establishing at staggering densities within a wetland and once bullfrogs reach adult size, they have very few natural predators in Washington.
“From a biological perspective, bullfrogs are formidable animals capable of adapting to a wide variety of environments and consuming quite literally anything they can fit in their mouths — which is why they are so problematic for our native wetland ecosystems,” said Riley Janquart, WDFW’s invasive herpetofauna strategist.
The threat from bullfrogs isn’t just predation; it’s also a numbers game. A single female can lay a mass of between 5,000 and 20,000 eggs in the water, allowing them to rapidly overwhelm native species. In Washington, recent evidence suggests that females may even lay multiple clutches in one season, a phenomenon that is already known to occur in lower latitudes of their range. Furthermore, there are significant concerns that bullfrogs act as vectors for diseases that can devastate local amphibian populations.
Bullfrogs were brought to Washington in the early 1900s, predominantly to support farms that harvested frog legs for food. Many of these frog farms failed and when they did, bullfrogs were released or escaped and became established in nearby wetlands. Bullfrogs were also introduced for sport, to add nostalgic summer frog calls to the landscape, and accidentally through fish stocking events. Bullfrogs have continued to establish and spread across Washington and now occupy a significant portion of the state’s low wetland habitat.
Today, they may continue to spread illegally through the aquarium and pet trades. Climate change is likely to exacerbate the spread of bullfrogs by increasing growing seasons and expanding suitable habitat.
American bullfrogs are officially classified as a Level 3 Prohibited Aquatic Animal Species (WAC 220–640–050) in Washington, which means this species may not be possessed alive, imported, purchased, sold, propagated, transported, or released into state waters.
WDFW works with a variety of partners to help control the population of bullfrogs across the state, especially to benefit vulnerable native species. In 2026, thanks to biodiversity funding via WDFW’s Wildlife Diversity Grants program, partners will continue to work on invasive bullfrog removal efforts at a variety of sites, including Nisqually National Wildlife Refuge and the Columbia River Gorge. These bullfrog control efforts are essential for persistence and recovery of endangered species like the northwestern pond turtle, Oregon spotted frog, and northern leopard frog.
“Although getting rid of all bullfrogs in Washington isn’t possible under current conditions, coordinated strategic efforts to suppress and eradicate populations impacting our native endangered species is necessary for the persistence and recovery of these species and ecosystems into the future,” Janquart said.
Here’s how you can distinguish an invasive bullfrog from native species like the endangered Oregon spotted frog:
- Ear fold: Unlike native frogs, bullfrogs have a unique fold of skin that runs from the eye, around the eardrum, and down to the shoulder — known as the supratympanic fold.
- No parallel lines: They lack dorsolateral folds, which are two distinct parallel lines or ridges of raised skin found on the backs of native frogs in Washington.
- The sound: Their call is an unmistakable deep, bass “jug-o’-rum” or “br-rum.”
How You Can Help
Conservation is a community effort. You can help protect our biodiverse wetlands by following these steps:
- Don’t let it loose: Never release unwanted pet frogs, tadpoles, or other species into the wild.
- Report sightings: If you spot an American bullfrog or an African clawed frog, report it to the Washington Invasive Species Council.
- Volunteer with WDFW: There may be opportunities to volunteer with WDFW as a bullfrog monitoring specialist to monitor for and lethally remove bullfrogs to benefit native species. Visit our website to learn more about volunteer opportunities.
