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Warming is Killing Yellowstone’s Amphibians, Researchers Find

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Disappearing ponds, lakes, and wetlands in Yellowstone National Park have caused a catastrophic decrease in the world’s oldest nature reserve’s frog and salamander populations, Stanford University researchers say.

Colombia spotted frog (Rana luteiventris), in Yellowstone National Park. Photo by Lauren Palumbi.

“Precipitous declines of purportedly unthreatened amphibians … indicate that the ecological effects of global warming are even more profound and are happening more rapidly than previously anticipated,” they wrote in a research paper published on the Web site of the Proceedings of the National Academy of Sciences.

Biology graduate student Sarah McMenamin spent three summers in a remote area of the park searching for frogs and salamanders in ponds that had been surveyed 15 years ago; Almost everywhere she looked, she found a catastrophic decrease in the population, Stanford said.

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“The amphibians need the ponds for their young to hatch, but high temperatures and drought are drying up the water. The frogs and salamanders lay eggs that have a gelatinous outer layer — basically ‘jelly eggs,'” McMenamin says — that leaves them completely unsuitable for gestation on land. If the ponds dry up, so do the eggs. “If there isn’t any water, then the animals simply don’t breed,” she says.

 

A tiger salamander (Ambystoma tigrinum) in Yellowstone.

 Photo by Sarah McMenamin

Biology Associate Professor Elizabeth Hadly, McMenamin’s graduate adviser and co-author of the paper, has worked in Yellowstone since 1981 and has witnessed the ponds going dry. “They’re just blinking off,” she said. “It’s depressing.”

The disappearing ponds lie in Yellowstone’s Lamar Valley, which holds dozens of small fishless ponds where the habitat has been ideal for the breeding and larval development of blotched tiger salamanders, boreal chorus frogs and Colombia spotted frogs.

As the world’s first national park, it is one of the most environmentally protected areas in the world.

The researchers studied climate and water records going back a century, ranging from handwritten logs of water flow in the Lamar River to satellite imagery, and could find no cause for the drying ponds other than a persistent change in temperature and precipitation. “It’s the cumulative effects of climate,” Hadly said.

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Stanford biology graduate student Sarah McMenamin surveying a pond in Yellowstone National Park for frogs and salamanders.

Photo by Yu-Jun Lee

Historically, the ponds–as small as backyard fish ponds, as large as small lakes–have been recharged during the summer by the groundwater in the soil, according to Stanford.

“But the water table is dropping,” the researchers say, “as human-induced climate change produces a deadly combination of higher temperatures and less rain and snow. Moreover, the seasonal wetlands near the ponds, usually ideal amphibian habitat, are evaporating earlier in the spring, the result of an earlier snowmelt.”

During the course of their study, the researchers monitored the loss of four amphibian communities because of pond drying. “Each event left hundreds of dried tiger salamander corpses behind. The ponds had dried rapidly, over just a few days, too fast for larvae to metamorphose and adults to migrate,” Stanford said.

“Everybody can identify with the loss of glaciers, but in Yellowstone the decrease in lakes and ponds and wetlands has been astounding,” said John Varley, the former chief scientist for Yellowstone. “What were considered permanent bodies of water, meaning reference was given to them in the 1850s, ’60s and ’70s, and bestowed with a name as a lake, are now gone. Some wetlands that were considered permanent ponds are no longer there. Some lakes have become ephemeral.”

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Lamar Valley, in northern Yellowstone, holds dozens of small fishless ponds where the habitat has been ideal for the breeding and larval development of blotched tiger salamanders, boreal chorus frogs and other amphibians. 

Photo courtesy Stanford University

Additional information:

Four out of Ten Amphibians in Decline, New Study Finds (NatGeo News Watch)

Frog Extinctions Linked to Global Warming (National Geographic News)

Frog Survival Linked to Eco-Health (National Geographic News)

Deadly Frog Fungus Spreads in Virus-Like Waves (National Geographic News)