Where Have the Amphibians Gone?

Since the late 1980s scientists have been concerned about the apparent decline in the number of amphibian populations across the landscape and in some instances, the disappearance of entire species. A recently published study* indicates that 72% of the 5743 known amphibians are in decline. Of these, 427 species are critically endangered. Globally, populations of only about 27% of the species are thought to be stable and fewer than 1% increasing. Amphibian populations in Rocky Mountain National Park may mirror this situation: one species has not been seen since 1974, one is in severe decline, and little information is available on the remaining three.

Five species of amphibians have been identified in the park, but Northern leopard frogs (Rana pipiens) have not been located in recent years and seem to have disappeared. Populations of boreal toads (Bufo boreas) have been in decline to the point that the boreal toad is listed as endangered by the State of Colorado (since 1993) and as "Warranted but Precluded" by the U.S. Fish & Wildlife Service (since 1995). While we don't know the reason for the decline of the leopard frogs, an amphibian chytrid fungus is implicated in the decline of boreal toads. We know that chorus frogs and wood frogs can also be infected with this disease and some researchers believe that tiger salamanders harbor the amphibian chytrid, but are not killed by it. If so, salamanders may be a source of this disease that proves deadly to other, less resistant amphibians.

USGS researchers conduct surveys in Rocky Mountain National Park each year as a part of the Department of Interior's efforts to understand amphibian populations on federal lands (the Amphibian Research and Monitoring Initiative), Western chorus frogs (Pseudacris triseriata)appear to be present in most areas of the park, but are absent in many areas that look like good habitat; wood frogs (Rana sylvatica) are found only on the west side of the park; and salamanders are apparently present in many habitats, but are seen less often than other amphibian species. Researchers are only beginning to be able to look at trends over time and while these amphibians appear to be doing alright in Rocky Mountain National Park, changes in the number of populations throughout the park may be occurring. Determining the status of amphibians is difficult; many species normally experience high flucuations in population size from year to year; species occur in remote areas of the park that are hard to get to; or, like salamanders, lack vocalizations, all characteristics that complicate accurate sampling.

If you would like to learn more about amphibians in and around Rocky Mountain National Park, the Colorado Division of Wildlife's interactive, web-based Colorado Herpetofaunal Atlas allows visitors to view photos, hear calls, see distribution maps, and enter observations of amphibians and reptiles. Visit the PARC - Partners in Amphibian and Reptile Conservation website to learn about the status of amphibians around the U.S.

*E. Stokstad, Science, 306, 391 (2004).

Last updated: March 31, 2012

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