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An evaluation of weather and disease as causes of decline in two populations of boreal toads

January 1, 2005

Two populations of boreal toads (Bufo boreas) experienced drastic declines in abundance in the late 1990s. Evidence supported the hypothesis of disease (the chytrid fungus, Batrachochytrium dendrobatidis) as the cause of these declines, but other hypotheses had not been evaluated. We used an 11-year capture–recapture data set to evaluate weather and disease as causes of these declines. We developed sets of mathematical models that reflected hypothesized relationships between several weather variables and annual survival rates of adult males in these populations. In addition, models that reflected the possibility that the declines were caused by an introduced fungus were developed. All models were fit to the data and were evaluated using a model selection criterion (QAICc). Our analysis provided strong support for the hypothesis of an introduced fungus and little support for the hypothesis that weather conditions caused the declines. Our results also suggest a strong, negative “marking effect” on survival rates of boreal toads. Model-averaged estimates of survival rate are presented.

Publication Year 2005
Title An evaluation of weather and disease as causes of decline in two populations of boreal toads
DOI 10.1890/05-0431
Authors Rick D. Scherer, Erin L. Muths, Barry R. Noon, Paul Stephen Corn
Publication Type Article
Publication Subtype Journal Article
Series Title Ecological Applications
Index ID 1015049
Record Source USGS Publications Warehouse
USGS Organization Fort Collins Science Center; Northern Rocky Mountain Science Center