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).
Habitat and Ecology
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.
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. As of August, 2007, even though some survey effort has taken place in the range there were not considered to be any other recent records from Costa Rica of this formerly common frog (Federico Bolaños pers. comm.). 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. 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. There might not be any subsequent records, indicating a decline and possible disappearance in this country, too.
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.
The species has been recorded from a number of protected areas in both Costa Rica and Panama. 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.
Red List Status
Critically Endangered (CR)
Listed as Critically Endangered because of a drastic population decline, estimated to be more than 80% over the last ten years, inferred from the apparent disappearance of most of the population, perhaps due to chytridiomycosis.
This species was previously included in the genus Hyla but has recently been moved to the new genus Isthmohyla (Faivovich et al. 2005).
Frank Solís, Roberto Ibáñez, Alan Pounds, Federico Bolaños, Gerardo Chaves, Karen Lips 2010. Isthmohyla rivularis. The IUCN Red List of Threatened Species 2010: e.T55627A11343375. http://dx.doi.org/10.2305/IUCN.UK.2010-2.RLTS.T55627A11343375.en