This species occurs below 700 m asl in scattered localities throughout northern and central Borneo (Kalimantan, Sabah, Sarawak, and Brunei Darussalam). It also occurs on Tawitawi Island in the Sulu Archipelago of the Philippines, where a record of this species (Diesmos and Leong pers. comm.) was previously incorrectly assigned to Microhyla annectens. It is not expected to occur more widely in the Philippines (A. Diesmos pers. comm. March 2018).
Habitat and Ecology
The species occurs in the leaf litter of lowland primary rainforest and it appears to be unable to adapt to modified habitats (I. Das. pers. comm. March 2018). It breeds in small pot-holes on rocky banks of clear streams and rivers, although breeding appears to occur only in certain nights. Its call is described by Dehling (2010).
The species is difficult to find due to its small size. It appears to be easier to find when it is breeding, however breeding appears to occur only in certain nights (Dehling 2010). Due to ongoing decline in the extent and quality of habitat, the population is suspected to be decreasing.
The principal threat to the species is habitat loss. In Indonesia this is caused by rapid clear-cutting of lowland tropical rainforest in forest concession land and for oil palm plantations (Indonesia Red List Assessment Workshop May 2017). The type locality in Sarawak has been destroyed by logging concessions which took place in the 1990s, so its occurrence there is unlikely (I. Das pers. comm. March 2018).
This species has been recorded from several protected areas, including Lanjak Entimau Wildlife Sanctuary, Batang Ai National Park, Bako National Park, Upper Baleh National Park, and Kubah National Park (Sarawak), Maliau Basin Conservation Area (Sabah), Ulu Temburong National Park (within the Batu Apoi Forest Reserve in Brunei), and Kayan Mentarang National Park, Sebuku Sembakung National Park, Betung Kerihun National Park, and Gunung Nyiut Nature Reserve (Kalimantan).
Effective preservation of lowland forest is needed to conserve this species because oil palm plantations are encroaching into protected areas in Kalimantan (Indonesia Red List Assessment Workshop May 2017). Some oil palm companies and forestry companies designate High Conservation Value areas, which is required by some financial institutions providing loans. However, not all lenders require these areas to be set aside and the habitat within the HCVs could disappear if the lender or requirements change (Indonesia Red List Assessment Workshop May 2017).
Further research on this species' distribution, population size and trends is recommended.
Red List Status
Near Threatened (NT)
Listed as Least Concern in view of its wide distribution and presumed large population. However, since this species depends on primary forest and there is ongoing decline in the extent and quality of these habitats due to widespread forest loss within its range, its population should be monitored.
IUCN SSC Amphibian Specialist Group 2018. Microhyla petrigena. The IUCN Red List of Threatened Species 2018: e.T57889A58478677. http://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T57889A58478677.en .Downloaded on 23 January 2019