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UBC Theses and Dissertations

Terrestrial Pacific giant salamanders (dicamptodon tenebrosus Good): natural history and their response to forest practices Johnston, Barbara


The Pacific Giant Salamander (Dicamptodon tenebrosus Good) is red listed, or considered endangered, in British Columbia. Habitat loss through forest harvesting poses the largest potential threat to the species' persistence in the province. Although studies have examined the ecology of larval Pacific Giant Salamanders, virtually nothing is known about the terrestrial phase of this species: their natural history, the effects of timber harvesting, or the efficacy of proposed management strategies. During the summer and fall of 1996 and 1997,1 used radio-telemetry to examine the movements and habitat use of terrestrial Pacific Giant Salamanders in forested habitat in south-western British Columbia and north-western Washington. By tracking animals in old growth, second growth, clearcut and buffered habitats, I also investigated the effects of clearcut logging on these animals, the efficacy of riparian buffer strips for their conservation, and their dispersal or recolonization ability. Terrestrial Pacific Giant Salamanders were found to be relatively sedentary creatures that spent the vast majority of their time in refugia such as burrows, rotten logs and streams. During the summer and fall, they wandered somewhat randomly throughout suitable habitat, showing no evidence of restricted home ranges or seasonal migrations. They were predominantly nocturnal, and their activity level was strongly associated with rain. The location of daytime refugia was associated with the availability of coarse woody debris, water, rock and leaf litter. Although the response of terrestrial PGS to forest practices was ambiguous, some study results suggested that terrestrial Pacific Giant Salamanders may be adversely affected by clearcut logging. Catch per unit effort was lower in clearcut habitat than in forested habitat, and animals inhabiting clearcuts appeared to adjust their behaviour in ways that reduced their risk of desiccation. Riparian buffer strips twenty to thirty meters in width appeared to be a promising management strategy for the conservation of terrestrial Pacific Giant Salamanders. Buffers seemed to maintain the relative abundance of terrestrial animals at levels comparable to those in forested habitat, and the movement patterns of animals in buffer strips were indistinguishable from those of animals found in continuous forest.

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