Nycticebus hilleri
Silhouette: Mareike C. Janiak · PhyloPic
In 3 days ~40% in a week ~70%
The Sumatran slow loris (Nycticebus hilleri) is a strepsirrhine primate and a species of slow loris that is native to Sumatra. While this species used to be considered a junior synonym of the Sunda slow loris, it is now recognized by the IUCN as a full species. This species is named after Hiram M. Hiller Jr., who collected the holotype of this species while exploring the East Indies in 1901. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Gunung Leuser National Park | 🇮🇩 Indonesia |
More parks will be added in future updates.
Possible
About 20% of wildlife watchers report a Sumatra Slow Loris sighting in Gunung Leuser National Park on a given day, based on 7 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 13th most-seen of the 19 mammals we can rate there. Over three days the chance rises to about 40%, and over a week to about 70%, if each day is a fresh chance.
April
In that month about 40% of wildlife watchers report a Sumatra Slow Loris in Gunung Leuser National Park on a given day, against under 5% in February–March, June–August and October–December, the lowest months.
Between 8 and 11 pm
Across all the parks we cover, that three-hour window holds the most Sumatra Slow Loris sightings with a recorded time, and about 9 in 10 of them come between 6 pm and 6 am: it is mostly seen at night.
Only Gunung Leuser National Park, in our data
Gunung Leuser National Park is the only park on Wallace's Line with enough records to rate Sumatra Slow Loris sightings: about 20% of wildlife watchers there report one on a given day.
Same order: Primates
The closest relatives of the Sumatra Slow Loris that you can see in Gunung Leuser National Park (order Primates) are Sumatran Orangutan (about 80%), Thomas’s Langur (about 80%) and Crab-eating Macaque (about 70%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Sumatra Slow Loris is recorded against all the mammals logged in Gunung Leuser National Park (7 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.
