Giant bullfrogs invade Vancouver Island

Catch of a 2-foot-long American bullfrog fuels concern about the spread of the invasive species; 'They're eating everything that will fit into their mouth'

Russ Schut poses with massive bullfrog.

The recent catch of an enormous bullfrog in a remote Vancouver Island pond has fueled concern that the voracious amphibians are spreading unchecked across the British Columbia island’s landscape.
Russ Schut, who was fishing in tiny Sproat Lake with a worm and bobber, hauled in the 2-foot-long American bullfrog and released it—after posing for a photograph—without knowing that it belonged to an invasive species that threatens native critters.
Because they’re not native to the Canadian southwest and have few natural predators, such as alligators, water snakes, and kingfishers in their native American southeast, some of the bullfrogs are growing to abnormally large sizes.
(American bullfrogs are the largest North American frogs and typically grow to about 7 inches, and weigh up to 1.5 pounds.)

Generic photo of an American bullfrog

“They’re big and voracious,” Gail Walin, of the Invasive Species Council of British Columbia,” told the Alberni Valley Times.
“And when you’ve got a species like that, that can basically out-eat some of the native species; it will take away the forage that native species would use and at times they can be aggressive on other smaller-sized, earlier life-cycle frogs.”
Stan Orchard, a Victoria-based bullfrog hunting contractor, told Canada’s National Post: “They’re eating salamanders and garter snakes and hatchling turtles … songbirds that come down to the water’s edge to drink, baby ducks, waterfowl … everything that will fit into their mouths.”
Walin believes that American bullfrogs might have been first introduced in or near Sproat Lake, at the south end of Vancouver Island, about five years ago. They’ve since been documented as far north as the Campbell River, about 150 miles from Port Alberni.
However, Orchard recalled a local sighting in 1989. As a herpetologist for the Royal B.C. Museum, he was sent to investigate reports of swimmers being frightened by tadpoles “the size of golf balls with big long tails on them.”
The University of Victoria is studying the rate of the bullfrogs’ spread. Walin theorized that they were first introduced by people emptying their aquariums, unaware of the environmental consequences.
“Whether it’s the plants in the aquarium, or the turtles, or the frog, they’re probably not native, and they can easily become established and take over the native population,” Walin said.
According to National Geographic, American bullfrogs can lay as many as 20,000 eggs, with tadpoles sometimes reaching lengths of 7 inches. A group of bullfrogs is called an army, or colony.
The voracious amphibians feed largely at night, ambushing prey by lunging with their powerful hind legs.
Though native to the American southwest, they now range throughout the continuous U.S., as far north as Canada and as far south as Mexico and Cuba. Their presence also has been documented in Europe, South America, and Asia.
So it seems that Vancouver Island is not likely to rid itself of the pesky frogs anytime soon. On the bright side, frog-gigging prospects are looking up.