But appearances are deceiving. Over the last decade, disaster has struck in the form of chytridiomycosis, or chytrid, a deadly fungal disease that has driven at least 200 of the world’s 6,700 amphibian species to extinction. One third of the world’s frogs, toads and salamanders are threatened. Forty percent are declining. Chytrid’s arrival has laid waste to the indigenous Sierra Nevada yellow-legged frog, Rana sierrae.
In Dusy Basin, a remote glacial valley in Sequoia and Kings Canyon National Parks a few miles west of Bishop Pass,Vance Vredenburg, a professor of biology at San Francisco State University, is conducting an experiment he hopes will help preserve what remains of these once abundant creatures. Dr. Vredenburg and his colleagues are inoculating chytrid-infected frogs with a bacteria, Janthinobacterium lividum, or J. liv, that does not prevent infection with chytrid but can help frogs survive.
Dr. Vredenburg, Reid Harris of James Madison University in Harrisonburg, Va., and colleagues found the symbiotic bacteria on several amphibian species. Lab experiments last year showed that J. liv produces a metabolite, violacein, that is toxic to the chytrid fungus. Dr. Vredenburg wants to see how effective the treatment will be in the wild.
Even before chytrid arrived, the Sierra frog population had been severely reduced by the California Department of Fish and Game’s practice of seeding high-elevation lakes with hatchery-raised fingerling trout for the sport fishing industry. Chytrid has hastened the destruction. Dr. Vredenburg and colleagues counted 512 populations scattered among the thousands of mountain lakes in the park in 1997. In 2009, 214 of these populations had gone extinct. A further 22 showed evidence of the disease. It is a far cry from the early 1900s, when frogs in the region were so common that lakeside visitors reported trampling them underfoot.
Dr. Vredenburg, 41, has been doing frog research in the Sierra since the mid-1990s. He chose frogs as research subjects because he wanted to do “basic science that could be applied toward solving some real-world problems, like the biodiversity crisis. Once your study animals start dying, believe me, you pay attention!” At the time, he said, “I saw many scientists as living and working in a bubble. Besides,” he added, “I like catching frogs.”
For his Ph.D. at the University of California, Berkeley, under the mentorship of David Wake, Dr. Vredenburg measured the effects introduced trout were having on mountain yellow-legged frog populations. The results were clear: They wreaked havoc. Brown and rainbow trout, not native at higher elevations, are voracious consumers of tadpoles. In 2001, as a result of work by Dr. Vredenburg and Roland Knapp of the Sierra Nevada Aquatic Research Laboratory, the state fish and game agency and the National Park Service began a gill netting project to remove them. In areas where trout were removed, frogs recovered.
Curtis Milliron, a senior biologist at the fish and game department, pointed out that historically the agency has played a dual, sometimes paradoxical role. “We’re both ecological stewards and recreational purveyors,” Mr. Milliron said. Although his agency is implicated in frog decline, now his charter is to create “a biodiversity management plan where we can maintain frog habitat and implement frog recovery.”
Leaders at the National Park Service, too, once felt that “we need to protect the national parks from research scientists,” said David Graber, chief scientist for the service’s Pacific West region. Scientists’ agendas were viewed as being at odds with the service’s mandate, which calls for conservation and preservation as well as making parks available for recreation. “Now it’s different,” Dr. Graber said. “Now all we care about are the massive frog die-offs. We’re passionate about conservation. We can’t wait for ‘survival of the fittest.’ ”
Dr. Vredenburg himself was “speechless” when the park service granted permission to carry out the J. liv experiment in Dusy Basin. “Then I had to start planning,” he said.
Dr. Vredenburg chose Dusy Basin for his experiment because chytrid is just arriving here. Unlike Sixty Lake Basin several miles to the south, where frogs went extinct within four years of the arrival of chytrid, Dusy Basin still has frogs. Biologists do not know what first brought chytrid to the Sierra. But Dr. Vredenburg’s research showed that chytrid spreads in a linear wave across the landscape, an infection pattern like that of human epidemics. Infection levels start out light, then increase to very high. Then there is a mass die-off.
In July, Dr. Vredenburg and his students captured and tagged 100 frogs, apparently the last remaining here, with transponder tags. They weighed and measured frogs, and they recorded the tag numbers using an electronic reader. The experimental group contained 80 frogs; 20 were designated controls. Dr. Vredenburg and his students placed experimental frogs in plastic containers for an hourlong bath in cultured J. liv — long enough for J. liv to colonize on frogs’ skins. They released the frogs into the ponds and streams where they had been captured.
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