Comparison of Size, Structure, and Distributional Patterns of Two Salamander Populations in Marion Lake, British Columbia

During 1968 and 1969, populations of Taricha granulosa and neotenous Ambystoma gracile were trapped and observed in Marion Lake, B.C. The adult T. granulosa and A. gracile populations were estimated respectively at 2450 and 14,500. It was estimated that there were about 45,000 A. gracile young of the 2nd year in the lake. These populations represent total lake biomasses of about 18 kg for Taricha and 408 kg for Ambystoma. The numbers of young larvae were not determined for either species. The A. gracile population was widely dispersed throughout the spring and summer. Density and size composition varied between areas with different vegetation and substratum. The T. granulosa distribution within the lake was highly contagious and changed through time. Although displaced animals returned to the areas where they were caught, the positions of their home ranges changed through time. Taricha granulosa entered the lake in April and May, showed evidence of wandering in midsummer, and left the lake in September and October. Fifty percent of adult A. gracile seen during the breeding season were metamorphosed and were found in the lake only during April and May. Neotenous adults remained in the lake all year, as did larvae of the 1st and 2nd years. Those larvae that metamorphosed did so in late August and early September. Ambystoma gracile grew rapidly in the lake, but no growth was seen in T. granulosa. No source of T. granulosa mortality was found in the lake, but A. gracile were preyed on by fish and diving bugs, and dead specimens were found on the lake bottom.