Andes Frog Population Declining Due To Deadly Fungus, Not Climate Change
Several studies have confirmed a rapid decline in amphibian populations across the globe, including frogs. For example, according to a U.S Geological Survey study released in May 2013, the annual rate of decline was estimated at 3.7 percent. At that rate, half of the amphibian population would be decimated within the next two decades. The report speculated that the decline could be attributed to climate change, drought, and/or disease.
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A new study published in the journal Conservation Biology, however, conclusively identifies the cause: a deadly fungus that thrives in the temperature zone of the Andes. While the research was conducted on the eastern slopes of the Andes near Manu National Park in Southern Peru, the results have implications for understanding the global decline in the population of frogs, according to Vance Vredenburg, co-author of study and associate professor of biology at San Francisco State University.
The researchers found that the culprit is a recently identified, deadly fungus Batrachochytrium dendrobatidis, or Bd, responsible for decline or extinction of nearly 200 frog species. Earlier studies had strongly suspected this pathogen for amphibian susceptibility.
The researchers first tested frogs' tolerance for climate change. They were exposed to varying water temperatures with their back flipped. If the frogs flipped back over, it meant they could tolerate the temperature, otherwise, it indicated that unable to deal with higher temperature, they were overwhelmed. The researchers also identified the optimal temperature under which Bd flourished. The study revealed that the frogs under study lived in the habitat with optimal temperature for Bd to thrive. The study suggested that "the fungus is driving a lot of the declines in this place" according to Alessandro Catenazzi, the lead author of the study from Southern Illinois University.
Yet, frogs in the lower elevations could be susceptible to climate change, not the fungus Bd, according to Vrendenburg. In other words, frogs at higher and lower elevations face different threats. Vrendeburg, who has closely studied the deadly pathogen Bd for over a decade, is worried that a Bd outbreak could "make bubonic plague look like a slight cough." His research shows that while some frog species are immune from Bd impacts, others are highly susceptible.
The study has several implications, according to Vredenburg. Conservation efforts, in his opinion should focus on limiting the spread of disease, most likely caused by human activity in that part of Andes. Also, the disease could have important consequences for human health. The focus of future research, according to Vrendenburg, should be on understanding how some species of Andean frogs are immune from pathogen Bd, so as to save the affected population of the frog from this deadly pathogen.
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