The Endangered Frog That Still Calls From Suwon's Rice Fields

Found only in South Korea, the Suwon tree frog has become one of the country’s rarest amphibians as wetlands and rice-field habitats continue to disappear. It is the only Class I endangered amphibian designated as endangered wildlife in Korea.

Although it closely resembles the common tree frog and is difficult to distinguish visually, the species has a distinctive call that allows researchers to identify it by sound alone. Experts consider the frog an “indicator species” that reflects the health of the surrounding ecosystem.

The frog was first discovered in a rice field in Suwon in the late 1970s. Suwon is a city in South Korea, and the species was named after the place where it was first identified. Its scientific name,

Dryophytes suweonensis

, also references Suwon. A researcher classified it as a new species after discovering that its call differed from that of the common tree frog.

The frog is highly sensitive to environmental change and is particularly vulnerable to pesticides, water pollution, and habitat destruction.

Perhaps for that reason, despite its name, the frog is now rarely found in Suwon. Urban development and habitat loss have steadily reduced the areas where it can survive. The frog is listed as Endangered (EN) on the IUCN Red List, and its remaining population is extremely small.

Nevertheless, several individuals continue to be observed each year in the Pyeong-ri fields area of Gwonseon-gu, Suwon, where the species was rediscovered. Will people continue to hear the call of the Suwon tree frog there in the future?

A Suwon tree frog with its yellow vocal sac visible. (Photo by National Institute of Ecology)/NewsPenguin

The species was first identified near the Rural Development Administration in Suwon. In 1977, Japanese herpetologist Mitsuru Kuramoto recognized the frog as a new species because of its distinctive call and officially gave it the name “Suwon tree frog” in 1980.

The frog measures around 2.5 to 4 centimeters in length. Compared to the common tree frog, it has a smaller body and shorter hind legs, while the webbing between its toes is less developed. Its back is bright green with a pale stripe running down the center, and brownish stripes extend from the nostrils along the sides of the body. Male frogs usually have yellow vocal sacs, though they may sometimes appear black.

Its most distinctive feature is its call. While common tree frogs produce a high-pitched “kwaek-kwaek” sound, the Suwon tree frog makes a lower, sharper “wong-wong” sound. Researchers say the metallic quality of the call is so distinctive that the species can often be identified by sound alone during field surveys.

The frogs usually begin their activity in April and breed between May and July. They mainly lay eggs in rice paddies and agricultural waterways. During the breeding season, males cling to rice stalks and call through the night to attract mates.

Rediscovered in Suwon’s Pyeong-ri Fields

Despite its unique name, the frog is now difficult to encounter in Suwon. Habitat degradation and urban expansion have significantly reduced its population. The species is now believed to survive only in limited areas of Gyeonggi and Chungcheong provinces.

In Suwon, the frog was rediscovered in 2012 in the Pyeong-ri fields area of Gwonseon-gu. Since then, Suwon City has promoted conservation policies centered around the area. Because the frogs mainly inhabit agricultural land — much of it privately owned — the city adopted a conservation approach based on farmers’ participation.

The city introduced environmentally friendly farming practices aimed at reducing pesticide and chemical fertilizer use. It has also supported farmers through snail farming methods and agricultural assistance programs so they can continue eco-friendly farming. The goal is to maintain farmland while preserving an environment where the frogs can survive.

Since 2019, Suwon City and the National Institute of Ecology (NIE) have conducted annual joint monitoring during the breeding season from May to June under a memorandum of understanding (MOU). According to Suwon City officials, four to five individuals have been observed annually in the Pyeong-ri area over the past three years.

City officials said that “the Suwon tree frog is a species highly sensitive to habitat conditions and has a very small population,” adding that “maintaining and managing existing natural habitats is the most important priority.” They also said the city is pursuing conservation policies through public-private cooperation.

A Suwon tree frog discovered in the Pyeong-ri fields of Suwon in 2023. (Photo by Suwon City)/NewsPenguin

Why Recovery Efforts Remain Challenging

The National Institute of Ecology is also conducting breeding and restoration research on the Suwon tree frog. However, because the species has such a small population and mainly inhabits farmland and wetlands under heavy development pressure, both research and restoration efforts remain difficult.

An official from the institute explained that “capturing endangered species or using them in breeding research requires government approval, and the number of individuals that can be secured from each region is limited.” The official added that “the Suwon tree frog is still facing difficulties at the breeding stage.”

They also explained that releasing frogs into the wild before securing a sufficient breeding population may produce limited results. In addition, releasing individuals into habitats that do not match their environmental conditions could lead to genetic disturbance or failure to adapt.

They stated that “restoring the Suwon tree frog is not simply a matter of releasing individuals into nature,” adding that “habitat conditions and genetic characteristics must also be carefully considered.”

“Conservation Requires Understanding the Frog’s Ecology”

Some experts argue that conservation efforts should move beyond simply maintaining existing habitats and toward discovering additional habitats and legally protecting them.

Kyo Soung Koo, a senior researcher at the Korea Institute of Environmental Geography, said current conservation policies remain focused on breeding-season surveys and rice paddies and therefore fail to reflect the frog’s broader ecology. He stressed that field-based ecological research and habitat creation, including reed fields and waterside wetlands, must accompany conservation efforts to sustain stable populations.

Dr. Koo explained that although the frogs use rice paddies during the breeding season, they also inhabit estuaries, streams, and irrigation channels and are especially active on reeds and surrounding vegetation near paddies. He compared the situation to “building only a kitchen for a chef and expecting them to live there.” In other words, conservation efforts must protect the species’ broader living environment.

A Suwon tree frog calling from atop a reed. (Photo by Kyo Soung Koo)/NewsPenguin

A Suwon tree frog active at night. (Photo by Kyo Soung Koo)/NewsPenguin

Professor Yikweon Jang of Ewha Womans University said that securing stable habitats is more important than simply increasing the number of individuals. He added that releasing frogs into the wild without suitable habitats would be meaningless and emphasized the need for protected areas and habitat restoration.

The disappearance of the Suwon tree frog would mean more than the loss of a single amphibian species. It would signal the decline of the rice paddies, wetlands, waterways, and broader ecosystems the frog depends on.

Whether people will continue to hear the calls of this small creature in Suwon’s rice fields may ultimately depend on how well those habitats are protected.

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