The Population Decline and Extinction of Darwin’s Frogs
Darwin’s Frogs are two species of frogs of the family Rhinodermatidae: Rhinoderma darwinii (also called the Southern Darwin’s frog) and Rhinoderma rufum (also known as Chile Darwin’s frog or Northern Darwin’s frog); the first native to Chile and Argentina and the second endemic to central Chile. Both frogs are named after Charles Darwin who had previously discovered it in Chile during his world voyage on the HMS Beagle.
A peculiarity of these frogs is that species are mouth-brooding and tadpoles develop inside the male vocal sac.
Rhinoderma darwinii is classified since 2004 as “Vulnerable" on the IUCN Red List and Rhinoderma rufum is listed as “Critically Endangered" since 2010. The main threats to these species are drought, pine forestry and clear-cutting of forest for R. darwinii, and he destruction of the native vegetation for R. rufum.
However, a study published in June 2013, developed by researchers at the University Andres Bello (Chile), University College London, Zoological Society of London and the University of Chile, which included extensive surveys carried out throughout the historical ranges of both species from 2008 to 2012, provide evidence that R. rufum is extinct and indicate that R. darwinii has declined to a much greater degree than previously recognized.
According with this study, the last sighting of R. rufum based on museum archives and the scientific literature, was in 1980. Although Rhinoderma darwini can still be found across a large part of its historical range, remaining populations are small and severely fragmented. Conservation efforts for this frog should be stepped up and the species re-classified as Endangered.
In addition, a later study (November, 2013) indicates that the amphibian disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis is also a factor in the decline of populations of Rhinoderma species.
Photos: Top - Specimen of Rhinoderma darwinii photographed by Eric LoPresti / Bottom: Distribution Maps of Rhinoderma spp. by Soto-Azat C, Valenzuela-Sánchez A, Collen B, Rowcliffe JM, Veloso A, (2013).