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Pacific Southwest Research Station
Tahoe Science Projects supported by SNPLMA
Effectiveness of reintroductions and probiotic treatment as tools to restore the endangered Sierra Nevada yellow-legged frog (Rana sierrae) to the Lake Tahoe Basin
Roland Knapp, University of California-Santa Barbara
The Sierra Nevada yellow-legged frog (Rana sierrae) was until recently a common inhabitant of the central and northern Sierra Nevada, including the Lake Tahoe Basin. Because of its abundance, R. sierrae played an important role in structuring aquatic and adjacent terrestrial ecosystems, with strong effects on nutrient cycling and food web dynamics. Unfortunately, due primarily to the introduction of non-native fish and a novel (but widespread) amphibian pathogen (Batrachochytrium dendrobatidis), R. sierrae is now absent from more than 90% of its historical range and may be extirpated from the Lake Tahoe Basin. Reversing this decline will depend critically on the removal of introduced fish from key habitats and on frog reintroductions. B. dendrobatidis infection has limited the success of previous R. sierrae reintroduction efforts, but a recently developed probiotic treatment against B. dendrobatidis may provide an effective method of minimizing disease impacts. In this study, we propose to test the effectiveness of reintroductions and probiotic treatment as tools to restore R. sierrae to the Lake Tahoe Basin. The frog treatment will involve augmenting the microbial community that inhabits the skin of R. sierrae with Janthinobacterium lividum, a bacterium that in recent laboratory and field trials was found to strongly inhibit the growth of B. dendrobatidis on amphibians, including R. sierrae. J. lividum is common in soil and water, and is found naturally at low density on the skin of R. sierrae. In the first year of the project, 10 adults and 160 juveniles will be translocated from source populations on the Eldorado National Forest to two lakes on the adjacent Lake Tahoe Basin Management Unit. The reintroduction lakes were recently returned to their natural fishless condition and contain high-quality habitat for R. sierrae. Prior to release at the reintroduction sites, some of the frogs will be treated with J. lividum and the remainder will serve as untreated controls. An additional 160 juveniles will be treated and translocated during the second year of the project. Following frog treatment and release, the effect of J. lividum treatment on disease status and survival of frogs will be quantified over a two year period using capture-recapture methods and radio-telemetry. This research will provide critical insights into the effectiveness of J. lividum treatment in increasing the survival of R. sierrae. If the treatment is effective, the study results could markedly increase the success of future R. sierrae reintroduction efforts and have broad implications for the recovery of this declining species in the Lake Tahoe Basin and throughout the Sierra Nevada.
Relation to Other Research Including SNPLMA Science Projects
The proposed project is closely tied to several recently-completed or ongoing projects designed to restore R. sierrae habitat and reverse the decline of this species. In 2008, the USDA Forest Service-Lake Tahoe Basin Management Unit (USFS-LTBMU) initiated a project to restore habitats for R. sierrae by removing non-native trout populations from eight lakes in the USFS-LTBMU portion of the Desolation Wilderness. At the inception of this project it was hoped that R. sierrae would naturally recolonize the target lakes following fish removal. When this did not occur, LTBMU staff initiated discussions with other agencies and scientists regarding the feasibility of reintroducing R. sierrae to these lakes, and those discussions led to the development of the current research project. Currently, a major limitation on the widespread use of reintroductions is the lack of information on what methods to use to maximize the success of reintroduction efforts. This new project will add considerably to understanding the extent to which chytridiomycosis limits reintroduction success and, if our J. lividum treatments are successful, will provide a critically important method by which to minimize the effects of B. dendrobatidis. As such, results from the proposed project could have broad implications for the design and implementation of future recovery actions undertaken on behalf of frogs across their range.
Expected date of final products:
|Last Modified: Mar 7, 2013 06:28:12 PM|