Jonathan Kolby

Investigation of Forest Canopies as Possible Safe Havens from Amphibian Chytrid Fungus (Batrachochytrium Dendrobatidis): Hope in the Midst of a Global Amphibian Extinction Crisis

Plectrohyla dasypus adult male.

Plectrohyla dasypus juvenile.

Plectrohyla exquisita adult male.

Town/RegionCountryCategoriesDate
Cusuco National ParkHondurasAmphibians, Central and Latin America, Marine29 Sep 2008

The amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd) is a rapidly emerging pathogen which is linked to the global decline and extinction of amphibians. Bd currently threatens the existence of nearly one third of all known amphibian species and poses one of the greatest conservation challenges of our time. Species susceptible to infection develop an often lethal condition known as chytridiomycosis. Many species have already vanished and hundreds more face imminent extinction due to this emerging infectious disease.

In 2007, I began surveying for this pathogen within Cusuco National Park, Honduras, a threatened cloud forest which is home to 14 species of endangered and critically endangered amphibians. My results established this rainforest to be the second known site of infection for the country and also showed a positive correlation between susceptible species and those reported to be experiencing enigmatic population declines by the IUCN Red List of Threatened Species. Due to these alarming results, I continued this investigation in 2008 and discovered additional endangered species to be infected.

Since Bd is a waterborne pathogen, most researchers do not consider arboreal amphibian species to be at risk as compared to those which rely upon permanent terrestrial water bodies. Regardless, in 2008 I documented Bd infection in several arboreal amphibian species in Honduras. The potential for Bd to fuel the extinction of arboreal species has not previously been considered and deserves urgent attention. To address this concern, this project will produce the first risk analysis of the threat which Bd poses to arboreal rainforest amphibians. By employing canopy access rope techniques, vertical data logger arrays will be deployed to monitor the environmental attributes which Bd would be exposed to when present in arboreal habitats. In addition, endangered arboreal amphibians will be radiotracked and their behavioral patterns closely monitored to determine the location of diurnal retreat sites. Despite the demonstrated presence of Bd in arboreal species, this investigation will also consider the possibility that selected retreat sites may provide safe havens from Bd if such locations possess chemical and physical attributes known to impede optimal Bd growth.

For more information contact J_Kolby@hotmail.com

Project Update: December 2009

We now have evidence that arboreal epidemics of amphibian chytrid fungus are certainly possible, and that this pathogen may affect ALL amphibians, despite life history pathways. We have now discovered infection in species with aquatic arboreal larvae (bromeliad frogs-Bromeliohyla bromeliacea) as well as direct-developing terrestrial larvae (salamanders of the genus Bolitoglossa). These groups of amphibians do not enter permanent water bodies, can be found any distance away from rivers, and obtain their moisture from the rainwater captured by bromeliads and other epiphytes. Interestingly, we did find the water within some bromeliads to be surprisingly acidic (as low as pH 3.3), but we also observed great variation between the water condition of bromeliads within any given location. Therefore, although some bromeliads within forest canopies might provide safe havens from amphibian chytrid fungus, others certainly do not. As such, we fear that the situation is more grave than expected: arboreal and semi-arboreal amphibian species are not protected by the condition of arboreal water bodies, nor do they experience decreased exposure by avoiding infected terrestrial water sources.

As interesting as all of our data are, the last statement is of greatest significance and I would very much like to pursue this further. I have already designed a substantial project to conduct during the summer of 2010 to continue this work. This past summer, we found chytrid-infected tadpoles within arboreal bromeliads and this literally blew my mind. The infections were severe and were exhibited by tadpoles completely confined to bromeliads, and these bromeliads were located some distances away from any terrestrial water source....meaning that something must have brought chytrid to the tadpole. Whereas adult amphibians can cause their exposure by virtue of their own locomotion, these tadpoles could not. Most people would think little of this and assume that an infected amphibian must have wandered from bromeliad to bromeliad, shedding infectious chytrid zoospores along the way, which subsequently infected my tadpoles. But in none of these immediate locations can you find ANY species of amphibians which enter terrestrial water sources, where chytrid is most likely to be acquired. Therefore, I believe that this pathogen is also spreading by wind and/or precipitation events (i.e. tropical storms), and hope to be the first to provide evidence of this dispersal mechanism; which carries with it global conservation implications.

Final Report

Read about the activities undertaken and findings of this project in the final report below.

File DownloadSize
Final Report.doc695.5 KB
Detailed Final Report.doc1.59 MB
2nd RSG Grant Awarded

Read about the latest developments in Jonathan's work http://www.ruffordsmallgrants.org/rsg/projects/jonathan_kolby_0


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