Kaloula borealis
In 3 days ~50% in a week ~80%
The boreal digging frog (Kaloula borealis) is a species of microhylid, or "narrow-mouthed," frog found in Northeast Asia. Its range covers much of central and northeastern China, the Korean Peninsula, and Jeju Island. Adult boreal digging frogs are roughly 4.5 cm in length, round in shape with toad-like speckled skin. Tadpoles are up to 35 mm (1.4 in) in length.
The boreal digging frog is common across much of its range, but is listed as an "Endangered category II species" in South Korea. It inhabits cultivated fields, including rice paddies, and is often found in close proximity to humanity, at altitudes of 10 to 900 m.
Boreal digging frogs breed during the annual rainy season, around June and July. After the rainy season is over they dig burrows underground, emerging only at night to feed. The eggs are laid in batches of 15–20 in monsoonal pools, with the tadpoles maturing within 30 days, much faster than most other frogs in this area. Wikipedia →
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China · 2026
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China · 2025
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South Korea · 2026
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| # | Park | Country | Daily sighting probability |
|---|
More parks will be added in future updates.
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | Zoológico La Era de las aves | 🇪🇸 Spain |
Possible
About 20% of wildlife watchers report a Boreal Digging Frog sighting in Nanjing on a given day, based on 34 verified sightings from GBIF citizen-science data. It is the 4th most-seen of the 11 amphibians we can rate there. Over three days the chance rises to about 50%, and over a week to about 80%, if each day is a fresh chance.
June and July
In those months about 40% of wildlife watchers report a Boreal Digging Frog in Nanjing on a given day, against under 5% in November to February, the lowest months. Those are among Nanjing's wettest months, with about 210 mm of rain a month against 40 mm in December.
Yes
Of the 6 cities where we can rate Boreal Digging Frog sightings, Nanjing has the highest daily chance: about 20%. Next come Daejeon (South Korea, about 20%) and Qingdao (China, about 20%).
Same family: Microhylidae
The closest relatives of the Boreal Digging Frog that you can see in Nanjing (family Microhylidae, Narrow-mouthed Frogs) are Ornate Chorus Frog (about 30%) and Arcuate-spotted Pygmy Frog (about 20%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Boreal Digging Frog is recorded against all the amphibians logged in Nanjing (34 verified sightings), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
