TIMES-COLONIST (Victoria, British Columbia) 24 November 04 Spring assault planned on bullfrogs (Norman Gidney)
A military-style campaign inspired by Alberta's rat patrol is shaping up for a spring offensive to stop invasive and voracious American bullfrogs from moving into more Victoria-area lakes.
The first assault is planned for the western front, a "control corridor" stretching about 10 kilometres sea-to-sea through the suburbs from Goldstream Park to Esquimalt Lagoon.
Workers wearing hip waders and armed with electroshock devices would stun the large frogs, then scoop them out in nets, while setting traps to take the smaller tadpoles. The frogs would probably be killed humanely by freezing, said consulting biologist Stan Orchard, an expert in the amphibians, who is promoting the idea.
The adult frogs can grow to the size of a dinner plate and have been entrenched in Elk and Beaver lakes for about 20 years, but in recent years the population has multiplied and frogs have been migrating west. They're now in Thetis, Florence and Langford lakes as well as smaller ponds.
"Langford just happens to be on the front line at the moment," said Orchard.
The next stop could be the Greater Victoria watershed which starts on Langford's west side, two kilometres from Langford Lake. The frogs carry a host of parasites, some of them known to transfer to humans, he said, and could create water-quality problems.
They are "absolutely voracious" predators and are altering the ecosystems of local lakes, competing with native species for food supplies. The adults will eat ducklings, small fish and turtles.
Orchard spoke to Langford's parks and recreation committee this week and convinced councillors and citizen members to vote a $5,000 grant toward the frog attack.
The big frogs could be eradicated if an organized multi-year campaign is mounted, he said in an interview. Volunteers alone aren't enough for the fight, he said.
The campaign would "hit these emerging populations very hard" starting in May, when warmer spring weather revives the frogs. Orchard said the corridor is a manageable size. "We can remove the frogs as fast as they invade."
Using another military metaphor, he said the frog-control plan would work back from the perimeter toward the big frogs' population centres in Beaver and Elk Lakes.
Unchecked, the frogs are taking over, he said.
"The frogs aren't just in the habitat, they are the habitat," said Orchard. The population densities are so high, "it's similar to creating a city of bullfrogs."
Twenty females can lay 400,000 eggs and most are surviving here, although it takes 31/2 years for tadpoles with tails and gills to metamorphose into juvenile frogs with lungs that breathe air.
With sponsorship by the Veins of Life Society, responsible for several waterway cleanup projects in the Victoria area, Orchard is trying to raise $50,000 for the bullfrog battle. Saanich provided a $1,600 seed grant earlier this year and Highlands residents passed the hat for $1,400.
Langford Coun. Denise Blackwell said she was out on Florence Lake in a boat this year and the frog problem was obvious. She urged Orchard to contact the Capital Regional District water district to co-operate in the battle.
B.C.'s population originated with breeders in the 1930s who released the amphibians after failed attempts at raising them commercially for frogs' legs.
Eradicating the American bullfrog here could take a decade or more, but Orchard pointed to Alberta, which began its rat-elimination program in the early 1950s and still spends $100,000 a year policing a 610-kilometre corridor along the Saskatchewan border.
Spring assault planned on bullfrogs