Darwin's Frogs Going Extinct from Deadly Fungal Infection

Scientists believe Darwin's frogs have gone extinct due to habitat loss and a deadly amphibian disease known as chytridiomycosis. Researchers from Chile's Universidad Andrés Bello (UNAB) and the Zoological Society of London report the loss of Darwin's frogs as one of only a few examples of "extinction by infection."

Darwin's frogs, named by Charles Darwin when he described the species in 1834 on an island just off Chile's west coast, are endemic to Chile and Argentina. The pointy nosed amphibians look like overstuffed leaves. Male Darwin's frogs have been observed scooping their own tadpoles up in their mouths and keeping as many as three inside their vocal sacs until the tadpoles mature into frogs.

The Northern Darwin's frog (Rhinoderma rufum) is presumed extinct, and the southern Darwin's frog (Rhinoderma darwinii) is in the midst of significant population decline, according to the Zoological Society of London (ZSL).

Habitat loss is credited as the main driver of the species' extinction, but the fungal disease chytridiomycosis appears to have driven the nail into the coffin, at least for the Northern Darwin's frog.

"Only a few examples of the 'extinction by infection' phenomenon exist. Although not entirely conclusive, the possibility of chytridiomycosis being associated with the extinction of the northern Darwin's frog gains further support with this study," said the ZSL's Andrew Cunningham.

To determine the presence of disease in the frogs, the researchers took specimens collected between 1835 and 1989 and tested their DNA for Batrachochytrium dendrobatidis (Bd), a fungus that causes the disease chytridiomycosis. An additional 26 populations of Darwin's frogs were sampled for Bd in Chile and Argentina between 2008 and 2012.

The results indicated a presence of the Bd fungus in the Darwin's frog population, which the scientists considered to be evidence that the chytridiomycosis disease is causing frog mortality in the wild.

"Amphibians have inhabited the earth for 365 million years, far longer than mammals. We may have already lost one species, the Northern Darwin's frog, but we cannot risk losing the other one. There is still time to protect this incredible species," said research leader Claudio Soto-Azat, from UNAB.

The researchers are working to further understand the reasons for the Darwin's frog extinction and the effects their absence may have on local ecosystems.

The researchers published their work in the journal PLOS One.