To assess amphibian and reptile populations to determine whether declining trends are regional or national, and to propose and evaluate hypotheses to explain declines.
Amphibians and reptiles are important components of ecosystems. Many species of amphibians have a complex life cycle with aquatic larvae and terrestrial adults. Population declines may reflect events in either aquatic or terrestrial environments or may integrate across the boundary between environments, making amphibians useful indicators of environmental change.
Large-scale declines of amphibian populations were first noticed among leopard frogs in the upper Midwest in the 1960s. More recently, serious declines have been observed in several anuran amphibians in western North America, and in anurans and salamanders in the East and Southeast. Some of these are now Federally endangered. The National Ecology Research Center has documented that leopard frogs and boreal toads are now absent from most known localities in the central Rocky Mountains.
The causes of most of the amphibian declines have yet to be determined, but anthropogenic contaminants have been implicated in several cases. Because amphibian species that were formerly widespread and abundant are now scarce, there is a clear need to assess the extent and nature of this threat to the biodiversity of North American vertebrates. This information on trends and causes of trends is required if wildlife managers are to prevent species from declining to the point where Federal listing is necessary.
These tasks will capitalize on ongoing research on amphibians by the National Ecology Research Center and provide immediate results and insight into this emerging problem. Reptiles would be added to research efforts in future years.
Submitted by R. B. Bury and P. S. Corn,
National Ecology Research Center, Fort Collins, Colorado
22 November 1989
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