Sylvirana mortenseni
Silhouette: Michael Scroggie, from original photograph by John Bettaso, USFWS (original photograph in public domain). · PhyloPic
In 3 days ~70% in a week ~90%
Sylvirana mortenseni is a species of true frog. It is found in Cambodia, Laos, and Thailand. The specific name mortenseni honours Ole Theodor Jensen Mortensen, the Danish zoologist who collected the holotype from the island of Koh Chang. Common names Mortensen's frog and Koh Chang Island frog have been proposed for it.
Sylvirana mortenseni has been recorded in evergreen forest on the lower slopes of the mountains, gallery forest, and heavily disturbed areas and forest edge habitats. It has been observed as high as 800 meters above sea level. Clear-cutting of forests is a threat to it, although it appears to also inhabit disturbed areas. Wikipedia →
Recording0:22
Thailand · 2011
© probreviceps · iNaturalist · CC BY-NC 4.0
Recording0:31
Thailand · 2025
© Niran Anurakpongsathorn · iNaturalist · CC BY-NC 4.0
Recording
Thailand · 2016
© Marc Anderson · Xeno · CC BY-NC-ND 4.0
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Khao Yai National Park | 🇹🇭 Thailand |
More parks will be added in future updates.
Possible
About 30% of wildlife watchers report a Mortensen's Frog sighting in Khao Yai National Park on a given day, based on 53 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the most-seen of the 13 amphibians we can rate there. Over three days the chance rises to about 70%, and over a week to about 90%, if each day is a fresh chance.
September
In that month about 60% of wildlife watchers report a Mortensen's Frog in Khao Yai National Park on a given day, against under 5% in January, the lowest month. That is one of Khao Yai National Park's wettest months, with about 330 mm of rain against 15 mm in December.
Between 2 and 5 pm
Across all the parks we cover, that three-hour window holds the most Mortensen's Frog sightings with a recorded time, and about 8 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Only Khao Yai National Park, in our data
Khao Yai National Park is the only park on Wallace's Line with enough records to rate Mortensen's Frog sightings: about 30% of wildlife watchers there report one on a given day.
GBIF citizen-science records
It is estimated from how often the Mortensen's Frog is recorded against all the amphibians logged in Khao Yai National Park (53 verified sightings from 2019 to 2026), 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.
