(Duméril & Bibron, 1841)
Darwin's frog (Rhinoderma darwinii), also called the Southern Darwin's frog is a rhinodermatid frog native to the forest streams of Chile and Argentina. It was first described by French Zoologist André Marie Constant Duméril and his assistant Gabriel Bibron, and is named after Charles Darwin who had previously discovered it in Chile during his world voyage on the HMS Beagle.
Darwin's frog is brown or green with a snout to vent length of 2.2 to 3.1 centimetres (0.9 to 1.2 in). The snout is elongated into a fleshy proboscis which gives the head a triangular shape. The limbs are relatively long and slender. The front feet are not webbed, but some of the toes on the back feet usually are. The dorsal surface is either uniform brown, tan or reddish brown, uniform pale or dark green, or some combination of brown and green with variable patterning. The ventral surface is black and white, with large blotches.
Darwin's frog feeds on insects and other arthropods. It not only has to hunt, but also must hide from predators wanting to eat it. Its most reliable technique to avoid its hunter is camouflage. It lies on the ground looking like a dead leaf until the predator passes by. Another defensive position is turning on the back and exposing the boldly patterned ventral surface.
The female Darwin's frog lays up to forty eggs among the leaf litter. The male guards them for about three weeks until the developing embryos begin to move and then he ingests the eggs and holds them in his vocal sac. They hatch about three days later and he continues to carry the tadpoles around in his vocal sac where they feed off their egg yolks and secretions produced by the wall of the sac until metamorphosis. At this stage, they hop out of the male's mouth and disperse.
Distribution and habitat
Darwin's frog is found in Chile and Argentina. In Chile its range extends from Concepción Province to Palena Province and in Argentina from Neuquén Province and Río Negro Province. It is found in glades and forested areas at altitudes of up to about 1,100 metres (3,600 ft) above sea level. It is also found in bogs and near slow-moving streams. It is found in a variety of vegetation types and it appears that a mixture of grassland, mossy areas, coarse woody debris and young trees and bushes in a mature native forest provides its optimum habitat requirements. Short vegetation increases the retention of water while decreasing the temperature of the soil and provides concealment from predators. The population is fragmented and this frog has poor dispersal ability.
Population decline and conservation status
Darwin's frog has undergone significant population declines due to habitat loss and degradation, largely from conversion of native forests to tree plantations. The amphibian disease chytridiomycosis, caused by Batrachochytrium dendrobatidis fungal infection, is also a probable factor, "particularly from the northern part of their historical range". Populations on Chiloé Island were found to be considerably more abundant than on the mainland.
The species is classified as Vulnerable on the IUCN Red List, and a 2013 study reported results of a population survey conducted from 2008–2012, which found the species at just 36 of 223 previously recorded habitat sites, with small populations at those sites. The study recommended IUCN Red List reclassification "at least as Endangered,” and provides a basis of comparison with future population surveys for further reclassification.
- Úbeda, Carmen; Veloso, Alberto; Núñez, Herman; Lavilla, Esteban (2008). "Rhinoderma darwinii". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 2 December 2013.
- Soto-Azat, Claudio; Valenzuela-Sánchez, Andrés; Clarke, Barry T.; Busse, Klaus; Ortiz, Juan Carlos; Barrientos, Carlos; Cunningham, Andrew A. (2013). "Is Chytridiomycosis Driving Darwin’s Frogs to Extinction?". PLoS ONE 8 (11): e79862. doi:10.1371/journal.pone.0079862. ISSN 1932-6203.
- Bell, Thomas (1843). Charles Darwin, ed. The Zoology of the Voyage of H.M.S. Beagle, Part V: Reptiles. London: Smith, Elder and Co. p. 48. Retrieved 1 December 2013.
- Duméril, A.M.C.; Bibron, G. (1841). Erpétologie Générale; ou, Histoire Naturelle Complète des Reptiles 8. Paris: Librairie Encyclopédique de Roret. p. 659. Retrieved 2 December 2013.
- Gratwicke, Brian; Soto-Azat, Claudio; Valenzuela-Sánchez, Andrés; Collen, Ben; Rowcliffe, J. Marcus; Veloso, Alberto; Cunningham, Andrew A. (2013). "The Population Decline and Extinction of Darwin’s Frogs". PLoS ONE 8 (6): e66957. doi:10.1371/journal.pone.0066957. ISSN 1932-6203.
- Fran Sandmeier; Kellie Whittaker (2008-09-08). "Rhinoderma darwinii". AmphibiaWeb. Retrieved 2013-12-06.
- Crump, M.L. (2003). Grzimek's Animal Life Encyclopedia, 2nd ed., Vol. 6 Amphibians, 175, Gale.
- Duellman, W.E., ed. (1999). Patterns of Distribution of Amphibians: A Global Perspective, 325, The Johns Hopkins University Press.
- Frost, D.R., ed. (1985). Amphibian Species of the World: A Taxonomic and Geographical Reference, 551, Allen Press, Inc. and the Association of Systematics Collections, Lawrence, Kansas.
- All About Frogs: Species Caresheets : Information on Specific Breeds of Frogs and Toads
- Strange Breeding: Darwin's Frog