McCranie’s robber frog

McCranie’s robber frog: An unfortunate name

The biologist James McCranie was not at all happy with the common name McCranie’s robber frog or McCranie’s Robber Frog that was given to the frog species Craugastor chrysozetetes. He would have preferred a name that reflected the species’ locality, such as Cerro Búfalo Streamside Frog. The reason: In addition to McCranie, the herpetologist Jay Mathers Savage and the zoologist Larry David Wilson were also involved in the original scientific description of Craugastor chrysozetetes in 1989.

Adult males of the species Craugastor chrysozetetes were around 3.4 to 4.1 centimeters long, while females were somewhat larger at 3.7 to 4.6 centimeters. McCranie’s robber frog had an olive-brown back; its belly and throat were pale lilac to lilac-brown with white spots on the chin. Pale blue spots adorned the chest area of female animals.

In addition to McCranie’s robber frog, the Corquin robber frog, which was native to Honduras and was also described by McCranie, Savage and Wilson in 1988, is extinct.

McCranie’s robber frog – fact sheet

alternative name	Cerro Búfalo streamside frog
scientific names	Craugastor chrysozetetes, Eleutherodactylus chrysozetetes, Craugastor (Campbellius) chrysozetetes
original distribution area	Honduras
time of extinction	1989 at the earliest
causes of extinction	Habitat loss, hurricane, fungal disease
IUCN status	critically endangered (possibly extinct)

Extinct between 1989 and 1995

McCranie’s robber frog lived at elevations of 880 to 1,130 meters in the premontane moist forest of the Cordillera Nombre de Dios in Honduras, a country in Central America. The frog species was native mainly to the region along the Quebara de Oro river.

Between 1980 and 1989, six expeditions took place in the Quebara de Oro area. Specimens of McCranie’s robber frog were found on four of them, including during what was, for the time being, the last visit to this region in 1989.

James McCranie did not return to this area until 1995, but he could no longer find any of the robber frogs. Scientists therefore carried out further searches in 1996, 2003 and 2005—without success.

Death through habitat destruction and chytrid fungus

The robber frog was last seen alive in 1989, according to McCranie in the Catalogue of American Amphibians and Reptiles in 2017. The species must have become extinct between August 1989 and February 1995. But why?

The deforestation of the forest to create cropland and the settlement of the region by humans probably played a decisive role here. In October 1998, torrential rainfall triggered by Hurricane Mitch also caused much larger landslides than had previously occurred. The reason was earlier human intervention in the ecosystem. These stream-altering landslides destroyed large parts of the Quebra de Oro, so that animals could no longer find a basis for life there.

McCranie also suspects that the fungal disease chytridiomycosis, which occurs exclusively in amphibians, may have contributed to the extinction of McCranie’s robber frog. Along the Quebra de Oro, experts found the chytrid fungus Batrachochytrium dendrobatidis in two of four frogs and toads (Anura) in 2003.

Is McCranie’s robber frog not extinct after all?

McCranie’s robber frog, already very rare during its lifetime and restricted to a small habitat, was listed as extinct in 2004 by the IUCN.

However, the IUCN changed this status in 2019 to critically endangered. Experts assume that McCranie’s robber frog may have survived in Pico Bonito National Park, which lies in the Cordillera Nombre de Dios.

The park, which was established in 1993 to protect the cloud forests, is characterized by lush flora and fauna. Since no habitat-altering measures have taken place there, there is a chance that a small population of the species Craugastor chrysozetetes has survived.

Hybrid form with another robber frog possible

During his expeditions in Honduras, McCranie found that Craugastor chrysozetetes and another robber frog species living there, Craugastor fecundus (Nombre de Dios streamside frog), were able to interbreed. McCranie also documented the hybrid forms resulting from the cross photographically.

The IUCN has also classified Craugastor fecundus as endangered or critically endangered, because this frog species too was last documented in 1989. If the species does actually still exist today, the same applies as for McCranie’s robber frog: It is most likely to be found in Pico Bonito National Park, where its population would then probably comprise fewer than 50 individuals.

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