Executive Summary

The magnitude of ecological problems created by populations of introduced and invasive bullfrogs is well-documented - summarized provincially by Orchard (1999) and internationally by Lannoo (1995). A population of bullfrogs was established about 25 years ago at Elk and Beaver Lakes in the Municipality of Saanich on southern Vancouver Island and they have since extended their distribution into the western Districts of Highlands and Langford (Map 1). Based upon all evidence, there is general agreement amongst conservation biologists that it is highly desirable to intensively manage and, where possible, eradicate introduced populations of this species. While it may be impractical to attempt to keep bullfrogs out of the Lower Mainland, extirpation and exclusion from southern Vancouver Island and the Gulf Islands is feasible, practical and warranted. The evidence is overwhelming that bullfrogs are detrimental to the survival of many native species and the sustainability of native aquatic, riparian and upland ecosystems. There are also legitimate concerns regarding water quality and nutrient cycling changes brought about by sudden population explosions of voracious bullfrogs and their tadpoles, particularly in nutrient poor (oligotrophic) lakes.

This program will establish a ‘control corridor’ extending from Finlayson Arm to Esquimalt Lagoon on southern Vancouver Island (Map 2). The purpose of the control corridor is: a) to remove as quickly as possible all bullfrogs and their tadpoles from within the control corridor; b ) to block the further westward spread of bullfrogs, particularly into the Greater Victoria Watershed; and, c) to contain existing populations within peninsular Victoria, so that they can be systematically eradicated in subsequent years.

A variety of humane, species specific, and eco-friendly trapping, capture and eradication techniques will be tailored to specific age-classes of frogs and tadpoles. Each technique will take advantage of the seasonal behaviour patterns of bullfrogs, and will adapt and optimize each technique for the variable habitat types that exist within the control corridor. Skills and knowledge derived from this program will have wide application both regionally and globally.

The program aims to:

  • Develop, trial and implement techniques and methodologies for the quick and total eradication of the American bullfrog populations within the control corridor;
  • Educate and train volunteers and the general community to participate in the implementation of the control and eradication program.
  • Establish technical capacity to map distributions and monitor populations on an on-going basis;
  • Provide a model for American bullfrog eradication programs elsewhere in North America and other jurisdictions around the world;
  • Develop materials, methods and networks to mobilize communities for environmental protection, locally and regionally.