Managing an Unpredicted and Unexpected Large Scale Amphibian Migration: Applying Hungarian Experience and Knowledge to Protect Western Toads on a British Columbia Highway

The plight of amphibians globally is becoming increasingly serious as the adverse impacts to their natural habitats caused by human development are being recognized. Throughout Europe and North America, formerly widespread indigenous amphibian species are becoming increasingly less common. The spatial distributions of some species, once considered ubiquitous throughout large regions of these continents, are becoming limited to progressively smaller and more isolated geographic areas. Where once, large expanses of undisturbed natural environments enabled amphibian populations to remain stable, human activities have resulted in extensive habitat fragmentation and reduced genetic diversity. The elimination of migratory routes between remaining habitats critical for the life cycle stages of amphibians has raised the significance of mitigating the impact of transportation corridors. While large mammals, such as deer, moose and elk have both the physical size and speed to avoid motor vehicles and trains; small, slow moving amphibians are completely vulnerable when attempting to cross transportation corridors. Large mammals can be protected from transportation corridors by the installation of wildlife exclusion fencing and critical habitat connectivity can be maintained to some degree by the construction of engineered crossing structures. Protecting amphibians is a more complicated task due to the greater number of species and their significantly wider range of physical sizes, movement patterns and life cycle characteristics. Consequently, species of amphibians co-existing in the same environments fragmented by transportation corridors may need a diverse range of mitigation strategies in order to survive. However, geographically distinct species from the same genus, with similar characteristics, such as physical size, migration radius, and migration patterns, may be protected with the same types of mitigation measures. In such cases, knowledge and experience collected while protecting a specific amphibian genus on one continent can effectively be used to protect the same genus on another continent. In August, 2007, the British Columbia Ministry of Transportation (BCMoT) was notified of an unpredicted and unexpected, large scale migration of Western toads (Bufo boreas) occurring across a major highway on Vancouver Island in British Columbia, Canada. Although extensive wildlife assessments conducted prior to the design and construction of the highway did not identify the potential for Western toads, an estimated one million toadlets were discovered converging on the highway. The migration was successfully managed in part with expertise developed by researchers at the Hungarian Danube Research Station of the Institute of Ecology and Botany of the Hungarian Academy of Sciences working to protect the same genus in Hungary. Temporary amphibian fencing was immediately installed and a collection system was developed. Approximately 950,000 toadlets were successfully recovered and transported across the highway. As a result of the migration, BCMoT developed a wildlife migration response protocol and initiated Western toad monitoring in the area. Similar migration events, with the same and other amphibian species, have the potential to occur at other locations in Europe and North America. The collection and dissemination of best practices can promote and facilitate the expedient use of existing experience and knowledge developed to protect amphibians on either continent.

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