Shasta Salamanders Surveys for the Shasta-Trinity National Forest (ver. 2.0, July 2020)

Abstract/Summary

The Shasta salamander (Hydromantes shastae) has been petitioned for listing under the Endangered Species Act. The greatest threat to the species is likely habitat loss that will be caused by the increase in elevation of Shasta Lake that will occur with proposed increases in the height of Shasta Dam to increase water storage capacity and maintain cold water for Chinook salmon (Oncorhynchus tshawytscha). Another potential threat is the fungus Batrachochytrium salamandrivorans, which has not yet been detected in North America but is lethal to related salamanders (Hydromantes strinatii) in Europe (Martel et al. 2014). In addition to these threats, recent genetic evidence suggests that the species as originally petitioned consists of three distinct species: H. shastae, H. samweli, and H. wintu (Bingham et al. 2018). Herein, we treat the species complex as a single entity because of difficulty distinguishing among the different species in the field. Recent work has increased knowledge about the habitat types within which Shasta salamanders can be found to include volcanic rock outcrops and areas of mature forest with scattered rocks, but no outcrops (Nauman and Olson 2004). To our knowledge, however, surveys to date have not accounted for the possibility of false absences, though Nauman and Olson (2004) used reference sites to ensure that Shasta salamanders were available on the surface to be detected. Systematic surveys that quantify and account for detection probabilities are needed to distinguish between true and false absences and their results would contribute information about habitat suitability and the distribution of the species. This information is vital to estimate what portion of the species complex would be lost to inundation when the elevation of Shasta Lake is raised and to identify potential refugia or recipient sites for translocations.

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