Wightman’s robber frog (Eleutherodactylus wightmanae)
|Also known as:||melodius coqui|
|Size||Female snout-vent length: 2 cm (2)|
Wightman’s robber frog is classified as Endangered (EN) on the IUCN Red List (1).
Wightman’s robber frog (Eleutherodactylus wightmanae) is an endangered amphibian found only in the upland forests of Puerto Rico. A rather small species, growing to a maximum length of just two centimetres, this diminutive frog has brown to grey mottled upperparts that often have a wash of pale pink or rose-yellow. There is sometimes an orange stripe along the sides of the robust body to the top of the head, and two black spots on the lower upperparts. There is a single dark bar on each thigh, and the vent is greenish-yellow, yellow or orange. The iris is golden or golden-grey. The male Wightman’s robber frog has a dark grey to black throat flecked with green (2).
Wightman’s robber frog is only found in the interior uplands of Puerto Rico (1).
A terrestrial species, Wightman’s robber frog occurs exclusively in mixed upland forest, and has not been recorded outside of this forest habitat (1).
Very little is known about the biology or behaviour of Wightman’s robber frog. However, the males are known to call in chorus on the ground, or whilst perched on an exposed rock or vegetation up to one and a half feet above the ground. The males call all day, with peaks in calling occurring at dusk and dawn. The typical call is a series of three to ten high-pitched whistles, with the first two and last couple of notes being lower in pitch and significantly quieter. If disturbed, Wightman’s robber frog will retreat under leaf litter (2).
Like other Eleutherodactylus frogs, Wightman’s robber frog lays its eggs in a humid rocky crevice. The hatched juveniles undergo direct development, meaning there is no aquatic larval stage (1) (3).
Already restricted in range, Wightman’s robber frog populations are in a continuing decline, estimated to be greater that 50 percent of the population over a ten year period (1). Threats to this species and its habitat include urban pollution, land clearing, forest burning and deforestation (1) (4).
However, evidence that this species is declining in even the best protected areas suggests that the most significant agent of decline is the fungal disease, chytridiomycosis (1) (5). This lethal disease is threatening amphibians worldwide, with high-elevation, stream-side species, such as Wightman’s robber frog, affected most severely (6). The spread of chytridiomycosis may be facilitated by rising temperatures and droughts associated with global climate change. During droughts, frogs are more likely to gather around remaining water sources, increasing the risk of infection (5). In addition, a further potential threat to Wightman’s robber frog associated with climate change is desiccation, particularly of juveniles, which occurs frequently during long dry periods (7).
Wightman’s robber frog populations have also been observed to decrease after hurricanes, which are a frequent destructive event in the Caribbean region (8).
Despite not being the target of any known conservation measures, Wightman’s robber frog is afforded a degree of protection in a number of well-managed protected areas. A major conservation priority for this species is further research into determining the cause of its decline (1). There is also a need for implementing a monitoring programme of populations, such that trends and responses to changes in habitat, as well as climate change and natural disturbances such as hurricanes, can be assessed (8).
For more information on amphibian conservation:
IUCN Amphibian Specialist Group:
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- Larval: of the stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
IUCN Red List (March, 2011)
- Schwartz, A. and Henderson, R.W. (1991) Amphibians and Reptiles of the West Indies: Descriptions, Distributions and Natural History. The University of Florida Press, Florida.
- Halliday, T. and Adler, K. (2002) The New Encyclopedia of Reptiles and Amphibians. Oxford University Press, Oxford.
- Stallard, R.F. (2001) Possible environmental factors underlying amphibian decline in eastern Puerto Rico: analysis of U.S. government data archives. Conservation Biology, 15: 943-953.
- Burrowes, P.A., Joglar, R.L. and Green, D.E. (2004) Potential causes for amphibian declines in Puerto Rico. Herpetologica, 60: 141-154.
- Stuart, S.N., Chanson, J. S. et al. (2004). Status and trends of amphibian declines and extinctions worldwide. Science, 306: 1783-1786.
- Stewart, M.M (1995) Climate driven population fluctuations in rain forest frogs. Journal of Herpetology, 29: 437-446.
- Viella, F.J. and Fogarty, J.H. (2005) Diversity and abundance of forest frogs (Anura: Leptodactylidae) before and after Hurricane Georges in the Cordillera Central of Puerto Rico. Caribbean Journal of Science, 41: 157-162.