Category Archives: Frogs

California Droughts and Wildfires Further Endanger Rare Mountain Frogs


Photo: Pacific Southwest Region USFWS

Fewer than 400 endangered yellow-legged mountain frogs now remain from the thousands that once crowded hundreds streams throughout California’s San Gabriel, San Bernardino and San Jacinto mountain ranges. Fifty years ago frogs swarmed these streams competing for desirable mates, but are now reduced to surviving in five hard-to-find streams that still trickle down despite five years of heavy droughts.

Scientists have grown more concerned about the frogs’ survival with a nearby wildfire growing each day, the third major fire in a month to overtake the frogs’ habitat. If this most recently endangered patch of vegetation is destroyed, biologists fear winter storms could wipe out the only remaining streams where the frogs live with debris and ash from previous fires. “I’ve never seen things this dry here before,” said Adam Backlin, a U.S. Geological Survey biologist, regarding a population of around 20 frogs in San Gabriel Mountains’ Big Rock Creek. “The last thing these frogs need is drought and wildfire.”

Though wildfires in the area have been common for a long time, they are now coupled with a vast array of factors that would make it difficult for sparse yellow-legged frog populations to recolonize from neighboring populations, as they did in decades past. Now, existing populations have been pushed to the brink of extinction by disease, urbanization, and widespread invasive predators from crayfish to trout and bullfrogs. Backlin notes that many isolated mountain yellow-legged frog populations were already decimated after 2003’s Old fire, 2009’s Station fire, and 2013’s Mountain fire, and are incredibly weak in the face of the most recent fire.


Just three weeks ago, the Sand fire destroyed 40,000 acres of northwestern San Gabriel Mountain watershed, containing sections of Soledad Canyon, a shelter to both rare arroyo toads and federally endangered unarmored threespine stickleback fish. This week, biologists were alarmed to discover that the Blue Cut fire burned through over 37,000 acres across San Gabriel’s northeastern canyons. They are now rushing to study the fire’s impacts on the yellow-legged mountain frogs’ populations, and questioning whether captive breeding may be the only way to ensure the species’ continued survival.

Federal wildlife authorities started a recovery program for the frogs back in 2010 that involves trout removal, captive breeding, and banning public access to regions where frogs still survive. Authorities hope to keep the frogs alive in carefully monitored aquariums at the San Diego and Los Angeles Zoos, where “insurance colonies” are being maintained with the help of the U.S. Fish and Wildlife Service. Omaha’s Henry Doorly Zoo, the Memphis Zoo, and the Santa Ana Zoo may join the program within the next year. Everyone involved hopes these efforts will allow the yellow-legged mountain frog to survive long-term, if outside its threatened natural habitat.


Source: Sahagun, Louis. “California’s drought, wildfires threaten endangered frog.” LA Times. 20 August 2016.

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Can Big Data Help Save the Red-Legged Frogs?


For years, Gary Kittleston has searched swamps for endangered red-legged frogs, waiting just after sunset. The environmental consultant now searches Watsonville Slough, a swamp east of Santa Cruz, California, with a headlamp and waders. Known by his nephews as “the frog whisperer,” Kittleston says that some years he’d be thrilled to find just one or two.

This marsh is a key habitat for red-legged frogs, who are an Endangered Species Act threatened creature due to overdevelopment of their habitats and over-hunting for their legs. A local land trust hired Kittleson to count the frogs to see if their population is growing or shrinking over the years.

This work is far from simple, however. Kittleson seeks out frogs within thick brush and listens for their low bellows amongst high-pitched cries of chorus frogs. Though the average listener would find the task nearly impossible, Kittleston has trained himself to hear red-legged frogs even while he’s speaking, searching for the telltale pattern of their call. “Chuck, chuck, chuck. It was three pulses,” he notes, determining one sound to be that of a red-legged frog.

Kittleston uses the traditional way of counting endangered animals, but this  takes up significant time and manpower, providing only a small slice of data for the time periods Kittleston or consultants like him can stand in each swamp. This is why the Land Trust of Santa Cruz County recently partnered with Conservation Metrics, a data company seeking to streamline the process of measuring endangered frog counts. Kittleson helped the company put up song meters around Watsonville Slough; each little green box has a microphone to capture the frogs’ chorus all night long. Conservation Metrics employees then load each night’s recordings into a computer and create algorithms that sift through hours of audio to pick out red-legged frog calls. This process allows one person and a computer to do what would normally require an entire team of field biologists, notes CEO Matthew McKown. “Our whole point is to make conservation better, so we are trying to make it as cheap as possible,” he says.

McKown created Conservation Metrics three years ago, hoping to help environmentalists keep more accurate records of threatened populations. He says that big data is now a hot tool in conservation that can help biologists study endangered animals and threatened habitats.”What you’re going to start having is cameras, acoustic sensors, satellites trained on these important parts of the world,” he says.

Meanwhile at the Watsonville Slough, Kittleson stands waist deep in swamp water. Night has fallen and he shines his headlamp around the marsh, searching for the piercing glare of frog eyes. One frog meets his gaze. “Beautiful. Adult red-legged frog,” Kittleson says. The frog perches atop a log that floats by the water’s edge. Though Kittleson isn’t hopeful about the future of this species, he says good data is the only way to tell if conservation efforts are making progress.


Source: Harnett, Sam. “Using Algorithms To Catch The Sounds Of Endangered Frogs.” KUNC. 31 May 2016.

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Resistance is not Futile


New research reveals that amphibians can acquire behavioral or immunological resistance to a deadly chytrid fungus implicated in global amphibian population declines.

Emerging fungal pathogens pose a greater threat to biodiversity than any other parasitic group, causing population declines of amphibians, bats, corals, bees and snakes. New research from the University of South Florida published in the journal Nature reveals that amphibians can acquire behavioral or immunological resistance to a deadly chytrid fungus implicated in global amphibian population declines.

“Acquired resistance is important because it is the basis of vaccination campaigns based on ‘herd immunity’, where immunization of a subset of individuals protects all from a pathogen,” said Jason Rohr, an associate professor of integrative biology who led the research team with Taegan McMahon, a USF alumnus who is now an assistant professor of biology at the University of Tampa.

One experiment in the study revealed that after just one exposure to the chytrid fungus, frogs learned to avoid the deadly pathogen. In subsequent experiments in which frogs could not avoid the fungus, frog immune responses improved with each fungal exposure and infection clearance, significantly reducing fungal growth and increasing the likelihood that the frogs survived subsequent chytrid infections.


“The amphibian chytrid fungus suppresses immune responses of amphibian hosts, so many researchers doubted that amphibians could acquire effective immunity against this pathogen,” Rohr said. “However, our results suggest that amphibians can acquire immunological resistance that overcomes chytrid-induced immunosuppression and increases their survival.”

Rohr also noted that “variation in the degree of acquired resistance might partly explain why fungal pathogens cause extinctions of some animal populations but not others.”

“The discovery of immunological resistance to this pathogenic fungus is an exciting fundamental breakthrough that offers hope, and a critical tool for dealing with the global epidemic affecting wild amphibian populations,” says Liz Blood, program officer in the National Science Foundation’s Directorate for Biological Sciences, which funded the research through its MacroSystems Biology Program.

Conservationists have collected hundreds of amphibian species threatened by the fungus and are maintaining them in captivity with the hope to someday re-establish them in the wild. However, reintroduction efforts so far have failed because of the persistence of the fungus at collection sites.

“A particularly exciting result from our research was that amphibian exposure to dead chytrid induced a similar magnitude of acquired resistance as exposure to the live fungus,” McMahon said.

“This suggests that exposure of water bodies or captive-bred amphibians to dead chytrid or chytrid antigens might offer a practical way to protect chytrid-naïve amphibian populations and to facilitate the reintroduction of captive-bred amphibians to locations in the wild where the fungus persists.”

“Immune responses to fungi are similar across vertebrates and many animals are capable of learning to avoid natural enemies,” Rohr emphasized. “Hence, our findings offer hope that amphibians and other wild animals threatened by fungal pathogens — such as bats, bees, and snakes — might be capable of acquiring resistance to fungi and thus might be rescued by management approaches based on herd immunity.”

Rohr cautioned, however, that “although this approach is promising, more research is needed to determine the success of this strategy.”

The above story is based on materials provided by University of South Florida (USF Health). Note: Materials may be edited for content and length.
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