The creaky calls of American bullfrogs resonate over the water all throughout King County, around White Center Heights Park, Marymoor Park, and Cottage Lake Park. Lithobates catesbeianus is a large-bodied frog found near the water’s edge or sunning itself in the center of ponds. For most people, seeing and hearing these amphibians around signals that our wetlands are healthy. But these critters aren’t actually native to Washington.  American bullfrogs were released in California as a potential food source and to help control insect populations more than 100 years ago and have now spread throughout the West, including King County.

Map of bullfrogs in King County

The introduction of American bullfrogs to western ecosystems has disrupted the lives of native organisms. In 2014, the American bullfrog was listed as one of the 100 most invasive species on the Global Invasive Species Database list of the 100 worst invasive species. American Bullfrogs are ravenous predators at almost all life stages. They devour small fish, aquatic invertebrates, young turtles, and other native amphibians.   

Each spring and summer, Woodland Park Zoo runs a community science project that supports native amphibians. Volunteers learn to identify adults, tadpoles, and egg masses of various species, then join a team to monitor breeding activity at specific locations. Over the years, the Amphibian Monitoring Project (AMP) has gathered data at several King County Parks, including the Klondike Marsh in Cougar Mountain Regional Park, and White River Countyline Levee Setback which is monitored by King County Department of Natural Resources Parks’ staff. Sally Lawrence co-leads the team monitoring Klondike Marsh with Hilary Barnes. Their team surveys a stretch of shoreline just north of Clay Pit Road, about a half mile in from Sky Country Trailhead, where beavers and a dam associated with old mining have created a vast, shallow wetland.  

Northern Pacific Tree Frog or Pseudacris regilla

If you’d like to learn more about native amphibians and volunteer to keep tabs on growing bullfrog populations, register to participate with AMP next year at monitoring@zoo.org.  

Article written by Jasmine Baker, a Project Dragonfly graduate student with Woodland Park Zoo’s Advanced Inquiry Program.