Invasive Species Alert:
American Bullfrog
By Liz Thompson, THPRD Natural Resources Maintenance Tech

The American bullfrog (Rana catesbeiana) is an introduced species in the Pacific Northwest that preys upon native amphibians and other fauna. These large frogs consume everything from tadpoles, insects and fish to ducklings, creating predation pressure on native species as well as competition for resources. Bullfrogs prefer warm, permanent ponds but can also be found foraging in ephemeral (seasonal) water bodies, small ditches and slow creeks.

THPRD’s Natural Resources Department is implementing a management program for the American bullfrog starting next month. This volunteer-based program will aim to remove egg masses of this invasive species. Bullfrog egg masses are different from native amphibian egg masses both in form and time of year they are found, so confusion between these and native amphibian egg masses is nearly impossible. Bullfrogs lay eggs in permanent water May through September, with the peak months being July and August, whereas native species lay in the winter months of January and February.

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