Bullfrogs and Biodiversity

Invasive species are those that do not originate in the area and cause harm to the local ecosystem. The American Bullfrog is native to Eastern and Central North American where they have natural predators that keep their numbers down. Outside of their native range, they are considered invasive predators that can cause serious harm to wetlands.

The American Bullfrog is widely considered one of the world’s most invasive species and a Bullfrog invasion is a serious concern to our sensitive wetland ecosystems that support species at risk in the Fraser Valley.

American Bullfrogs are the largest frog species found in BC, and in the Fraser Valley, these invasive frogs are at the top of the wetland food chain. Adults have voracious appetites and are generalist “gape-limited” predators, meaning they will eat anything that will fit in their mouths. This includes invertebrates, other frogs, salamanders, young turtles, snakes, birds and small mammals. Bullfrog tadpoles are herbivorous, consuming algae and detritus, and competing with other native species tadpoles.

In the photo below we see an adult female Bullfrog posed with a juvenile Bullfrog. The juvenile Bullfrog is already the size of an adult Northern Red-legged Frog.

American bullfrogs were originally introduced to BC by humans creating frog leg farms for human consumption. Once a few escaped or were released from these farms they have spread quickly to other areas. Humans contribute to the spread of Bullfrogs in BC by collecting and moving unknown wild frogs, using live tadpoles as fish bait, and releasing pets into the wild. Bullfrogs are also able to travel great distances over land and can thrive in human-disturbed habitats, making them very adaptable to changes in their environment. Once established in an area, populations can rapidly increase with just a few successful breeding seasons. A single female can lay between 5,000 to 20,000 eggs per year.

Pictured: young adult Green Frogs (another non-native species in the Fraser Valley) collected by children.