Glandirana rugosa
In 3 days ~30% in a week ~60%
The Japanese wrinkled frog (Glandirana rugosa) is a species of true frog native to Japan and introduced to Hawaii in the late 19th century. It has sometimes been regarded as a single species with the Imienpo Station frog (Glandirana emeljanovi) which is found on the East Asian mainland. The two species are distinguished from others by their rough and uneven skin. It lives and breeds in various freshwater environments, including ponds, streams and wetlands. The IUCN does not consider this species to be faced by any significant threats.
Populations of G. rugosa are of particular scientific interest because they display both male (XX/XY) and female (ZZ/ZW) heterogamety in different parts of Japan. This coexistence of two sex-determination systems within a single species makes the frog an important model for understanding the evolution and turnover of sex chromosomes in vertebrates. Genetic and cytogenetic studies have shown that its sex chromosomes, derived from the same ancestral pair, have undergone multiple independent differentiation and "recycling" events through recombination and hybridization.
Phylogeographic analyses have revealed deep genetic divisions between eastern and western populations, suggesting potential cryptic speciation within what is currently recognized as G. rugosa. The species remains common across most of Japan, particularly in rice paddies and small freshwater systems, and continues to be listed as Least Concern on the IUCN Red List. Wikipedia →
Recording0:09
United States · 2025
© smartinbiologist · iNaturalist · CC BY-NC 4.0
| # | Park | Country | Daily sighting probability |
|---|
More parks will be added in future updates.
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Osaka | 🇯🇵 Japan |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | Ueno Zoological Gardens (West Garden) | 🇯🇵 Japan | |
| 2 | Oita Marine Palace Aquarium | 🇯🇵 Japan |
With luck
About 10% of wildlife watchers report a Wrinkled Frog sighting in Osaka on a given day, based on 37 verified sightings from GBIF citizen-science data. It is the 2nd most-seen of the 8 amphibians we can rate there. Over three days the chance rises to about 30%, and over a week to about 60%, if each day is a fresh chance.
June to September
In those months about 20% of wildlife watchers report a Wrinkled Frog in Osaka on a given day, against under 5% in October to March, the lowest months. Those are among Osaka's wettest months, with about 180 mm of rain a month against 55 mm in January.
Only Osaka, in our data
Osaka is the only city on Wallace's Line with enough records to rate Wrinkled Frog sightings: about 10% of wildlife watchers there report one on a given day.
Same family: Ranidae
The closest relatives of the Wrinkled Frog that you can see in Osaka (family Ranidae, Typical Frogs) are American Bullfrog (about 20%), Black-spotted Frog (about 10%) and Japanese Brown Frog (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Wrinkled Frog is recorded against all the amphibians logged in Osaka (37 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.
