The Bully Frog

Late at night in the forest, the predator emerges from its cold, dark pond. Glistening yellow-green with dark patches, the eight-inch-long giant lets out a deep, echoing more-rum! and begins the evening's hunt.

California's largest frog, the bullfrog was introduced west of the Rockies from the eastern United States in the late 1800s for its meaty legs. Today, the invasive species can be found in nearly every pond, lake, and slow-moving stream below 4,000 feet elevation in the state.

Feeding mainly at night, bullfrogs prey on earthworms, insects, and even small snakes, birds, and mammals. They are taking a toll on native amphibian species as they feast on the eggs and young of spadefoot toads, red-legged frogs, and yellow-legged frogs.

After mating from February to July (depending on latitude), females lay a disc-shaped, gelatinous mass of up to 20,000 eggs among submerged plants or brush or on the water's surface. In about five days, tiny tadpoles hatch and feed mainly on algae until they are ready to metamorphose in about two years. The young frogs take about three years to reach maximum size and reproductive maturity.

Bullfrog resting on lily pad.
Photo: © 1998 Joyce Gross

 

American Bullfrog, Rana catesbeiana, in larval or
tadpole stage.
Photo: © 2000 John White
Adult bullfrog.
Photo: © 2002 William Flaxington