Save The Frogs Research Project on Chytrid Fungus in California Published

In 2015, SAVE THE FROGS! received a grant from the Alameda County Fish & Game Commission to research disease outbreaks in Foothill Yellow-Legged Frogs (Rana boylii) in the San Francisco Bay Area. The research was published in the journal Ecosphere. You can read the abstract below, or download the PDF of the publication here.

rana boylii alameda creek sarah kupferberg
Photo of gravid female Rana boylii from Alameda Creek by Dr. Sarah Kupferberg

Extreme drought, host density, sex, and bullfrogs influence fungal pathogen infection in a declining lotic amphibian.
Andrea J. Adams, Sarah J. Kupferberg, Mark Q. Wilber, Allan P. Pessier, Marcia Grefsrud , Steve Bobzien, Vance T. Vredenburg and Cheryl J. Briggs
Ecosphere. March 2017. Volume 8(3). Article e01740

Freshwater biodiversity is imperiled across the globe, and multiple stressors such as habitat alteration, non-native species invasion, disease, and climate change can act in concert to threaten vulnerable taxa. The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd), which causes the disease chytridiomycosis, is one of the causative factors of severe amphibian declines. The foothill yellow-legged frog (Rana boylii) is a stream-breeding anuran endemic to California and Oregon (USA) that has declined precipitously in recent decades, yet there is little information on its susceptibility to Bd. In the fall of 2013, we observed dead and dying juvenile R. boylii in a San Francisco Bay Area watershed where annual amphibian breeding censuses have been conducted since 1997 in a free-flowing reach and since 2003 in an anthropogenically modified stream reach. High pathogen loads on R. boylii and histologic lesions observed on a dead R. boylii metamorph collected from the site were consistent with lethal chytridiomycosis. The outbreak coincided with extremely low stream flows in autumn that concentrated frogs in drying pools and the absence of high peak flows in winter that allowed non-native American bullfrogs (Rana catesbeiana) to expand their spatial distribution in the stream network. Following the outbreak, we surveyed R. boylii and sympatric anurans at the site for the next two years to determine Bd trends within the population. Using mixed-effects models, we found that bullfrog presence was a positive predictor of both Bd prevalence and Bd load in R. boylii. Prevalence was also influenced by sex and life stage: Adult males were more likely to be infected than either females or juveniles. Moreover, we found that stream flow volume was negatively associated with Bd load. These results indicate that disease, drought, and flow regulation may interact synergistically to impact amphibians in ways not previously recognized, informing stream flow management strategies for native aquatic taxa.



Protocol for the Detection of Chytrid Fungus Using Quantitative PCR Techinques

In terms of its effect on biodiversity, chytridiomycosis is quite possibly the worst disease in recorded history. The disease, caused by a pathogenic chytrid fungus, has caused amphibian population declines in Australia, South America, North America, Central America, New Zealand, Europe, and Africa, and is likely responsible for over 100 species extinctions since the 1970's.

While chytridiomycosis has become a major focus of amphibian research worldwide, few herpetologists have any background in the laboratory techniques necessary to detect the chytrid fungus, and training classes are rare. Quantitative PCR (qPCR) is the most technologically advanced method of diagnosing chytrid infections, and the ability to perform qPCR in one’s own laboratory would both expedite the processing of samples and decrease the costs incurred by sending samples to private laboratories for diagnosis.

SAVE THE FROGS! has now made publicly and freely available a detailed protocol for the detection and quantification of Batrachochytrium dendrobatidis. This is the most in-depth protocol of its kind in existence, and can be found, along with accompanying slideshow, videos and supplementary materials at:

The slideshow, videos, webpage and other materials were developed as part of a free course offered by SAVE THE FROGS! and the Herpetological Circle of Panama. The course, entitled "Instruction and application of quantitative PCR molecular techniques for the study of amphibian epidemics", took place at the Smithsonian Tropical Research Institute in Panama City on October 5th-9th 2009, and was attended by 25 scientists from Panama, Colombia, and Costa Rica. Amphibian population in all three countries have experienced severe declines in numbers due to the chytrid fungus. This course was taught in Spanish by SAVE THE FROGS! Founder & Executive Director Dr. Kerry Kriger, with the valuable assistance of Vicky Flechas of Colombia's Universidad de Los Andes. This course effectively doubled the number of scientists on the planet capable of using quantitative PCR for the diagnosis of amphibian chytrid infections.

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"I've loved amphibians since I was born. Spent my childhood in mud and ponds with newts, salamanders, fish, frogs, snakes and bugs. I love water and adore amphibians. There's something about them that is amazing and perfect more than anything else on Earth."

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