ABSTRACT: The distribution of the Rocky Mountain tailed frog (Ascaphus montanus) in relation to the fluvial system: implications for management and conservation.

CGRG Bibliography of Canadian Geomorphology
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Abstract

The mating, egg-laying, and larval development of tailed frogs occur in dynamic mountain streams. During the lengthy (up to 5 years) aquatic residency these species are vulnerable to channel disturbances that can be exacerbated by land uses. Researches have highlighted specific tailed frog habitat associations but never in the context of fluvial system processes. Based on an extensive regional study with a watershed-wide sampling strategy, we demonstrate that the Rocky mountain tailed frog is limited to contributing basins of roughly 0.3-100 km2 in size, with peak numbers in basins up to 35 km2. We conclude that the prmary determinant of tailed frog distribution patterns in a watershed is basin area, a proximate variable for channel process domain and regional stream discharge: tailed frogs are adapted to cascade and step-pool channel morphologies because they afford more bedform stability and pore-space refugia than do smaller, colluvial headwaters, or larger floodplain forming plane-bed and pool-riffle bedforms of mainstem rivers. Secondarily, climate and physiography interact to influence occurrence and abundance at the watershed level by controlling such variables as runoff, water temperature and sedimentation regime. This point has important implications because it forces us to recognize that in complex systems, wildlife habitat associations are contingent on site-specific interactions amongst control variables: significance levels of any one variable to tailed frog distribution will not neccessarily be consistent among basins. The study clearly shows that case studies can produce conflicting results when they lack a process-based understanding of ecological response.

Bibliography of Canadian Geomorphology