This species is found in the mountains of the Central Cordilleras and Sierra Madres of northern Luzon Island, in the Philippines. It is restricted to elevations from 700–1,800 m asl in the Cordilleras, but has been found from sea level to 600 m asl in the Sierra Madres (Alcala and Brown 1998, Diesmos et al. 2014). This species is much more widely distributed than originally assumed (Brown et al. 2012).
Habitat and Ecology
The primary habitats for this fossorial species are lower montane and lowland forests, including streams and rivers. This species calls in large choruses in temporary pools following heavy rains (June–August) and breeding occurs in ephemeral pools (Brown et al. 2013). It is commonly found in disturbed habitats, such as agricultural land, rice paddies and gardens, adjacent to forested areas (A. Diesmos pers. comm. May 2017). It is known to occur at high abundances in disturbed habitats at many sites, provided that surveys are conducted at the beginning of the rainy season following heavy rains, when individuals emerge from the ground to breed (Brown et al. 2012).
This species is common wherever it is found in both forest and human-modified habitats, but has a very localized distribution. It may be undetectable if field surveys are conducted in dry months (Brown et al. 2012). The population trend is unknown.
The most important threat to this species is the deforestation of lower montane and lowland forests in the Cordilleras, and the pollution of streams and rivers. The montane forests are either being cleared for commercial-scale vegetable farms or are being developed into real estate.
In the Sierra Madre, the major threat is habitat loss due to small-scale shifting agriculture, expanding human settlements, wood collection for firewood and charcoal production, and illegal logging by commercial entities.
The species' range overlaps with the boundaries of several protected areas on Luzon Island and some of these are well-managed by the Department of Environment and Natural Resources in partnership with local government units. Since the 2004 assessment, in collaboration with various regional academic institutions, NGO-led awareness campaigns have been taking place to educate the public regarding the need to protect remaining forests on Luzon Island, resulting in positive responses by local communities and improved protection for priority species.
Improved enforcement of protected area boundaries and appropriate management practices are required to safeguard the remaining habitat, as well as ongoing awareness campaigns to raise public support.
More information is needed on this species' population size, distribution, and trends, and additional taxonomic research is recommended in light of the cryptic species present in this complex.
Red List Status
Listed as Least Concern in view of its relatively wide distribution, tolerance of a degree of habitat modification and presumed large population.
This is a species complex which may comprise at least two distinct evolutionary lineages (Philippines Red List Assessment Workshop May 2017).
IUCN SSC Amphibian Specialist Group 2018. Kaloula rigida. The IUCN Red List of Threatened Species 2018: e.T57856A58478297. http://dx.doi.org/10.2305/IUCN.UK.2018-1.RLTS.T57856A58478297.en .Downloaded on 19 January 2019