Coastal BC Animals: America Bullfrog

American Bullfrog

An American Bullfrog on Powell Lake BC.

Invasive species? Illegal immigrant? Whatever you want to call it, the Bullfrog is not native to British Columbia, and it's not benign. Here in Powell Lake we have the American Bullfrog.

Bullfrogs are native to eastern North America from Canada to Florida. Much like fish farming, Bullfrogs was imported to farm for their meaty legs. From there, they spread throughout the southern mainland and southeast Vancouver Island.

Females are larger than males and can grow to be 20 cm long and 750 grams in weights (8"/1.5 lbs). Males have a large tympanum (ear) behind the eye. Females have a smaller one. This is probably a female.

One way to distinguish a Bullfrog from a Green Frog (also invasive) is the fold of skin over the typanum. A Bullfrog's wraps around the tympanum, but the Green Frog's forms a long skin fold along the back.

Bullfrog tadpoles are large, dark-green, and can grow up to 15 cm long. They can stay in the tadpole stage for up to two years. For this reason, Bullfrogs need to breed in water sources that remain filled all year. Bullfrogs can live up to ten years.

The biggest problem with Bullfrogs is that they take over the territory of native species, often by eating their rivals. They are voracious and will eat anything that will fit in their mouths. That would include the beautiful little Pacific Chorus Frog I saw earlier this summer. Large Bullfrog tadpoles also present a problem, taking food sources away from tadpoles of native frog species.

You can help their further spread. Do not transport either live adults or tadpoles. If you notice a new colony of Bullfrogs developing, contact BC Frogwatch. -- Margy

Reference: B.C. Frogwatch Program (online)