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Distributional Changes and Population Status for Amphibians in the Eastern Mojave Desert

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Abstract:A number of amphibian species historically inhabited sparsely distributed wetlands in the Mojave Desert of western North America, habitats that have been dramatically altered or eliminated as a result of human activities. The population status and distributional changes for amphibians were investigated in a 20,000 km2 area in the eastern Mojave Desert in two ways.
For upland sites, where wetland habitat consists almost exclusively of spring encounter surveys were conducted at 128 sites in 1997-1999, and these results were compared to historical (pre.: 1970) lacality records. For lowland sites, i.e., sites in the major valleys and river flood plains, locality records and field observations were reviewed and compared between recent and historical times. Amphibians were found at 79% of the upland sites. By far the most common species was the red-spotted toad (73% of sites), followed by the Pacific chorus frog, Woodhouse's toad, relict leopard frog, and the introduced American bullfrog. Taxa recently observed or collected in the lowlands were Woodhouse's toad, Pacific chorus frog, American bullfrog, and the introduced tiger salamander. Taxa with historical records but no evidence of occurrence in the study area within the past five decades are the Vegas Valley leopard frog, Arizona toad, Great Plains toad, and Great Basin spadefoot. The amphibian fauna of the study area has changed dramatically in the past century, primarily at lowland sites where habitat loss and modification have been extreme. Striking changes are the nearly complete replacement of native leopard frogs (i.e., Vegas Valley and relict leopard frogs) by the introduced bullfrog, and the complete replacement of the Arizona toad in Las Vegas Valley by Woodhouse ' s toad or hybrids with predominantly Woodhouse's traits. In contrast, the distributions of two species characteristic of upland springs, red-spotted toad and Pacific chorus frog, appear to have changed relatively little from their historic distributions, despite consiuderable habitat modification at many sites.
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Citation:Bradford, D. F., J. R. Jaeger, and S. A. Shanahan. Distributional Changes and Population Status for Amphibians in the Eastern Mojave Desert. Western North American Naturalist 65(4):462-472, (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: Journal
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Published: 12/12/2005
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Downloads:
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Bullet Item Distributional Changes and Population Status for Amphibians in the Eastern Mojave Desert.PDF
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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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