This species appears to have the largest geographic range of any species in the genus. It is known from Cerro San Felipe and adjacent upland areas in the Sierra Alaopaneca, from the Sierra de Cuatro Venados, and from the Sierra de Coicoyán, north-central Oaxaca, Mexico, at 2,590-3,185m asl.
Habitat and Ecology
It inhabits cloud forest and mixed forests, living under bark or under fallen trees. It does not adapt well to significant degradation of its habitat. It is terrestrial and reproduces by direct development.
The species was once common on Cerro San Felipe (the type locality), but it is now only found in small numbers there. It is consistently observed at two sites in the Sierra de Cuatro Venados, but again at small numbers.
The reasons for the dramatic and enigmatic decline of this species is not known. The species is also being negatively impacted by agricultural expansion, human settlements, and logging, all of which are taking place extensively within its range. However, these threats do not explain the level of decline that has been observed, since the habitat is still in quite good condition in some places.
It occurs in Parque Nacional Benito Suarez, but there is still an urgent need to conserve the cloud forest remnants that remain in the Sierra de Juarez. Research is also needed to establish the reasons for the dramatic population decline; especially to see if this is related to a disease event. This species is protected by Mexican law under the "Special Protection" category (Pr).
Red List Status
Critically Endangered (CR)
Listed as Critically Endangered because of drastic population declines in excess of 80% that have been observed, are not understood, and may continue; and because its Extent of Occurrence is probably less than 100 km2, its distribution is severely fragmented, and there is continuing decline in the extent and quality of its habitat, and in the number of mature individuals.
Gabriela Parra-Olea, David Wake, James Hanken 2008. Thorius narisovalis. The IUCN Red List of Threatened Species 2008: e.T59421A11937624. http://dx.doi.org/10.2305/IUCN.UK.2008.RLTS.T59421A11937624.en .Downloaded on 19 November 2018