This is a very narrowly distributed species, restricted to the lowlands of western central Korea on an area of 30 km by 50 km (Yang et al. 2001, Kim et al. 2012). Its elevational range varies from 8-90 m asl (A. Borzee pers. comm. March 2014). Although remnant population could hypothetically be found on western lowlands of both South and North Korea, the range is not considered to be much greater than currently understood. Its current extant range, taken as a proxy for extent of occurrence (EOO), is estimated to be 4,031 km
Habitat and Ecology
It has been observed in paddy fields. Larval development requires access to standing water and the species has not been observed breeding in natural wetlands, although anthropologically altered wetlands such as rice paddies are acceptable breeding grounds (A. Borzee pers. comm. March 2014). Both this species and the related H. japonica rely on the same habitat for breeding, and there is a microhabitat selection preventing a large recruitment of H. suweonensis females and increasing the risk of hybridization (A. Borzee pers. comm. March 2014).
It is considered to be a rare species, with calling indexes developed by the North American Amphibian Monitoring Program peaking during the first three weeks of May at a significantly lower maximum that the calling indexes of the related H. japonica (A. Borzee pers. comm. March 2014). The totality of its population appears to be severely fragmented because its range matches with the metropolitan city of Seoul, and it is difficult if not impossible for individuals to disperse between patches due to distance and landscape elements (A. Borzee pers. comm. March 2014). A population estimate in 2012 covering several dozen localities, although not including all subpopulations, led to the conclusion that only 260 calling males are remaining (Kim et al. 2012). Assuming a sex ratio of 1:1, the population size could therefore oscillate around 500-600. The main part of the global population is found in Gyeonggi province while some additional subpopulations are found in the provinces of south and north Chungcheong and Gangwon provinces (A. Borzee pers. comm. March 2014). Previously known subpopulations in Suweon, Kangwa Island and Pyeongtaek have gone extinct during the last decade, and it is estimated that there has been a 50% population size reduction in this period (A. Borzee pers. comm. March 2014). Based on knowledge from closely related Palearctic tree frog species with similar ecologies, its generation length is estimated to vary between 1-3 years (A. Borzee pers. comm. March 2014). Using available information from the last decade, a 20-50% continuing population decline is projected to occur over the next two generations should there be no changes to its habitat (A. Borzee pers. comm. March 2014).
It is not known from any protected areas. Since 2012 this treefrog has been considered an endangered species by the Ministry of Environment of the Republic of Korea (Ministry of Environment of the Republic of Korea 2012). Habitat protection is urgently needed to assist the persistence of this species. Population monitoring is required to monitor trends across its global population.
This is a distinct species from the sympatric Hyla japonica (Kuramoto 1984, Lee and Park 1992, Yang and Park 1998, Lee et al. 1999, Jang et al. 2011, Borzée et al. 2013).
IUCN SSC Amphibian Specialist Group 2014. Hyla suweonensis. In: IUCN 2014