Electro-Frogging: An Innovative Technique for Capturing Invasive American Bullfrogs

Wildlife managers around the world mostly agree that populations of the alien invasive American bullfrog Rana (Lithobates) catesbeiana are a predatory menace to native species in and around lakes and ponds.  The extraordinarily wide and well-documented diversity of invertebrates and vertebrates recorded in the bullfrog’s diet include many endangered and economically important species.  The bullfrog’s rapid population growth and rates of geographical expansion also add compelling reasons to control or eliminate bullfrog populations quickly and thoroughly.  However the greatest obstacle thus far to eradicating bullfrogs has been failure to innovate on the strategic and technical side and thereby demonstrate that eradication is a feasible and practical option.  Historically, the application of laborious, costly, primitive and inefficient techniques - e.g. gigging (spearing), shooting, netting, pit fall trapping, grasping by hand, pond draining, habitat destruction - has created a widespread pessimism about any prospects for success.  In 2005 a program on southern Vancouver Island began with the aim of developing, testing and refining innovative and practical strategies, tools and tactics for removing bullfrogs faster than they can reproduce and faster than they can re-invade.  The approach was to test the feasibility of adapting electro-fishing technology specifically to the manual capture of American bullfrogs.  Beginning in 2007 with a beta-version of an 'electro-frogger' pole one 2-person team began capturing and removing juvenile and adult bullfrogs from various lakes and ponds.  By 2010, working from the water at night, a single team had removed over 15,000 bullfrogs from about 70 lakes and ponds on southern Vancouver Island.  We now have numerous case studies of ‘site control’ and ‘site eradication’ demonstrating that the management and control of this species is feasible and practical and that individual lakes and ponds can be made bullfrog-free in 4 years or less with only a few nights of effort per site per year.  The annual cost of keeping one team in the field throughout the bullfrog’s active season – approximately 120 nights of fieldwork per year - is about $50,000.