Bullfrogs

The bullfrog, Rana catesbeiana, is a very large introduced frog species out-competing and threatening smaller native species of amphibians in British Columbia.

            Bullfrogs, which are most active at night, are avid predators of our native frogs and many other animals, including small mammals and birds. As their numbers grow, they continue to threaten our native species, by competing for space in breeding areas and eating both the tadpoles and adult frogs.  Bullfrog tadpoles also feed on the same algae as the native tadpoles, so they are also competing for food.

Toads can often be confused with young bullfrogs because of their dry, warty skin. There is one native species of toad on Vancouver Island, the Western Toad, a rare beneficial species, and its call is easily distinguishable from that of the invasive bullfrog. The call of our Western Toad is a quiet chirping, while the bullfrog makes a loud, deep sound.

Click the speaker to listen to the Bullfrog Call
              400kb wav. file

Bullfrogs were brought to Vancouver Island beginning in the 1930’s as stock for frog farms interested in providing a supply of frog legs to restaurants. When farms and restaurants were unsuccessful, the frogs escaped or were released into the wild. Small isolated populations have been present near Victoria, in Cedar - Yellow Point near Nanaimo and in Coombs - Hilliers in the Parksville - Qualicum area for many years. They were first reported spreading into the Parksville area in the summer of 1976 and began spreading rapidly in other areas at about the same time, possibly in relation to human population growth, land clearing and subdivision development.

In 2000, bullfrog tadpoles were noticed in a small tributary of the Chase River in Nanaimo and soon after over 1000 tadpoles were removed from a small stormwater retention pond! Female bullfrogs lay floating egg masses containing up to 20,000 eggs. In some summers, the females may lay two batches of eggs, which take only 3-5 days to hatch in warm water. Therefore it is imperative to destroy the egg masses as soon as possible.

For a number of years GBEARS volunteers continued to remove adult bullfrogs, egg masses, and tadpoles from the pond in the headwaters of this small tributary. Our objective was to prevent bullfrogs from becoming established in this pond, but it soon became apparent that they were already well established in the surrounding area and would continue to re-invade the pond each winter and spring indefinitely. With no funding support for the costs of ongoing removal or a more comprehensive control and management program in the area, we eventually had little choice but to reluctantly abandon further removal and control efforts.

What Can You Do? 
  Do not move any frogs or tadpoles from one area to another!

  If any bullfrogs are seen or their loud, deep calls are heard near wetlands, ponds, or lakes in British Columbia, please report to the BC Ministry of Environment at (250) 751-3100.

For more information, visit our Bullfrog Links.

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Last modified: 02/02/09