Taxonomic notes: This species was previously included in the genus Hyla but has recently been moved to the new genus Isthmohyla (Faivovich et al. 2005).

This species occurs on the slopes of the cordilleras (Tilarán, Central and Talamanca) of Costa Rica and adjacent western Panama, from 1,210-2,040 m asl (Savage 2002). Its range, taken as a proxy for extent of occurrence (EOO), is estimated at 6,940 km².

In Costa Rica, it was presumed to have disappeared from Monteverde, Tapantí, and Las Tablas where it once was common. It was last seen in 1993 at Las Tablas and had apparently disappeared from Monteverde by 1989. More recent news from Andrew Gray and Mark Wainwright (in litt. To Bruce Young, September 2007; http://news.bbc.co.uk/2/hi/science/nature/7609780.stm), reported the rediscovery of this species at the Tropical Science Center Monteverde Cloud Forest Preserve, with several males being heard. The species was also relocated in Las Tablas in July 2010 (Alex Villegas, personal communication August 2010). As of 2013, the species has been recently recorded at three sites in Costa Rica, Monteverde, Las Tablas, and Cerro Chompipe (G. Chaves and A. García, pers. comm. 2013). In Panama, there are records from the Bajo Mono highlands of Chiriquí in 1982, and from Las Tablas in the early 1990s, but it had disappeared from the latter site by 1996. More recently, the species has been recorded from the Pacific slopes and Caribbean slopes in western Panama (Hertz et al. 2012). 

This species occurs along or in clear streams in lower and premontane rainforest. Males call at night from riparian bushes and herbaceous vegetation at the margin of or overhanging fast-moving mountain streams. Amplexus and egg deposition have not been observed in this species; tadpoles have been collected from streams.

There are no reports of this species being utilized.

The overall decline in this species is probably taking place as a result of infection of populations with the chytrid pathogen. Within Panama, it is threatened by general habitat loss through agriculture and selective logging.

• 2.1.3 Agro-industry farming
• 8.2 Problematic native species/diseases
• 5.3.5 Motivation Unknown/Unrecorded
• 2.1.2 Small-holder farming
• 1.1 Housing & urban areas

In the past, the species has been recorded from a number of protected areas in both Costa Rica and Panama. Currently, it is known to still occur in Monteverde and Parque Internacional La Amistad. Further research is urgently needed into the population status of this species. Given the threat of chytridiomycosis, recommended conservation measures likely should include the establishment of a captive-breeding programme.

• 3.4.1 Captive breeding/artificial propagation
• 1.2 Resource & habitat protection

Given available information, this species does not qualify as Critically Endangered or Endangered. There are no available data demonstrating continuing declines (within the last 10 years) or information on population fragmentation. However, recent survey efforts have recorded individuals in 5 disparate locations within Costa Rica and Panama, allowing the species to qualify as vulnerable under criterion D.

• Duellman, W.E. 1970. The Hylid Frogs of Middle America. University of Kansas Museum of Natural History, Lawrence, Kansas.
• Duellman, W.E. 2001. The Hylid Frogs of Middle America. Society for the Study of Amphibians and Reptiles, Ithaca, New York, USA.
• Faivovich, J., Haddad, C.F.B., Garcia, P.C.O., Frost, D.R., Campbell, J.A. and Wheeler, W.C. 2005. Systematic review of the frog family Hylidae, with special reference to Hylinae: Phylogenetic analysis and taxonomic revision. Bulletin of the American Museum of Natural History 294: 1-240.
• Ibáñez, R., Solís, F., Jaramillo, C. and Rand, S. 2000. An overview of the herpetology of Panama. In: J.D. Johnson, R.G. Webb and O.A. Flores-Villela (eds), Mesoamerican Herpetology: Systematics, Zoogeography and Conservation, pp. 159-170. The University of Texas at El Paso, El Paso, Texas.
• Lips, K.R. 1998. Decline of a tropical montane amphibian fauna. Conservation Biology 12: 106-117.
• Morelle, R. 2008. World's 'rarest tree frog' found. Available at: http://news.bbc.co.uk/2/hi/science/nature/7609780.stm. (Accessed: Oct 28).
• Myers, C.W. and Duellman, W.E. 1982. A new species of Hyla from Cerro Colorado, and other tree frog records and geographical notes from western Panama. American Museum Novitates 2752: 1-32.
• Pounds, J.A., Fogden, M.P.L., Savage, J.M. and Gorman, G.C. 1997. Tests of null models for amphibian declines on a tropical mountain. Conservation Biology 11: 1307-1322.
• Savage, J.M. 2002. The Amphibians and Reptiles of Costa Rica: A Herpetofauna between two Continents, between two Seas. University of Chicago Press, Chicago.
• Young, B., Sedaghatkish, G., Roca, E. and Fuenmayor, Q. 1999. El Estatus de la Conservación de la Herpetofauna de Panamá: Resumen del Primer Taller Internacional sobre la Herpetofauna de Panamá. The Nature Conservancy, Arlington, Virginia.