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Invasive Reptiles and Amphibians

American Bullfrog

  • Scientific Name

    Lithobates catesbeianus - Visit ITIS for full scientific classification. 

  • Description


    • Large frogs, can grow up to 8 inches in length, and can weigh up to 2.5 pounds.
    • Wide heads, thick bodies, long hind legs and webbed feet.
    • Large visible eardrums.
    • Smooth skin.
    • Green to brown color on backs, dark spots, and a cream to yellow colored belly.
    • Large tadpoles that can grow up to 6.5 inches in length. 
  • Habitat
    • Extremely adaptable creatures, found in a wide range of habitats, both natural and man-made.
    • Typically found around permanent water, which is necessary for successful reproduction but young frogs and dispersing individuals may be found around temporary water sources.
    • Prefers warm temperatures, but can withstand conditions below freezing by burrowing into the sediment.
    • Usually found in still, or slow-flowing waters.
  • Invasion Pathways and Distribution
    • Initially introduced in some areas for human consumption.
    • Can spread by natural dispersal, and through accidental inclusion in fish stock.
    • May also spread through escape or release from research facilities, aquariums, or by pet owners.
    • They can spread naturally by swimming through rivers and streams, and can be carried by water flow during flood events.
    • Native to the eastern U.S., but now widely distributed throughout California.
    • See USGS for a map of current U.S. distribution. 
  • Life History
    • Bullfrog breeding occurs in the warmer months within vegetation beds of permanent water bodies.
    • Males are very territorial, and fight over the best egg-laying sites. Eggs are laid in sheets that create rafts on the water surface.
    • Tadpoles eat algae, small animals, and small tadpoles of other frog species. 
  • Impacts
    • Consumes almost anything it comes across including: birds, rodents, snakes, turtles, frogs, crayfish, other invertebrates, etc.
    • Tadpoles can eat tadpoles of other frog species.
    • Strong ability to consume and outcompete native frogs and other native species.
    • Can spread a potentially fatal skin disease (Chytridiomycosis) to native frog species. 
  • References and Useful Links

    For references by category and links to other useful AIS sites see our Learn More page.