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Factors Implicated in Amphibian Population Declines in the United States

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Abstract:Factors adversely affecting amphibian populations in the US were evaluated using information from species accounts written in a standardized format by multiple authors (Volume 2 of this book). For each species, factors implicated by the authors (i.e., known or suspected) as affecting the persistence of populations were identified. Each species was also classified by status with regards to change in its historical geographic range or number of sites within the range, and region of the US. Information was sufficient to classify the status of 81 % of the 91 anuran species native to the US, and 61% of the 176 native caudate species. Species classified as Major Decline or Some Extirpations (collectively referred to as adversely affected species) comprised 49% of the anurans and 38% of the caudates. Approximately a quarter of the species were classified as No Change for both anurans (26%) and caudates (23%), and relatively few species were classified as Increase (5% of anurans and 0% of caudates). The frequency of adversely affected species was exceptionally high for ranids in the western US, whereas no differences in frequency of adversely affected anurans were evident among non-western ranids, western non-ranids, and non-western non-ranids. Specific adverse factors were identified for 58% (53) of the 91 anurans and 53% (93 ) of the 176 caudates. Of the species with adverse factors implicated, land use was the most frequently implicated for both anurans (77% of the 53 species) and caudates (91% of the 93 species). Exotic species were the second most frequently 40 - implicated adverse factor for anurans and third for caudates (IO%). Chemical contamination ranked third for anurans (I 9%) and second for caudates (I7%). Less frequently implicated factors were disease, water source modification, collecting/harvesting, and UV-B radiation. Among the anurans with adverse factors implicated, exotic species were implicated significantly more frequently in the western US (76% of 21 species) than in the other regions (16% of 32 species). Among caudates chemical contamination was implicated significantly more frequently in the non-western US (23% of 65 species) than the western US (4% of 28 species).
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Citation:Bradford, D. F. Factors Implicated in Amphibian Population Declines in the United States.Michael Lannoo (ed.), Lannoo, M.J. (ed) Declining Amphibians: A United States Repsonse to the Global Problem, Chapter23. University of California Press at Berkeley, Berkeley, CA, (2005).
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Contact: Chris Siebert - (702) 798-2234 or siebert.christopher@epa.gov
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Division: Environmental Sciences Division
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Branch: Landscape Ecology Branch
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Product Type: Book Chaptr
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Published: 08/12/2005
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Bullet Item Factors Implicated in Amphibian Population Declines in the United States
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Related Entries:
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Bullet Item Development of Landscape Indicators for Use in Regional Ecological Risk Assessments
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