Camera trap photograph of a Sumatran tiger in the Leuser ecosystem, Indonesia.
Phil et al. 2025, BKSDA, DLHK
A camera trap study found more than double the number of critically endangered Sumatran tigers than studies found elsewhere on the Indonesian island, a positive sign for conservation efforts.
Sumatran tigers are the last remaining population of the subspecies. Panther tiger sondaikaone of two tiger subspecies according to recent taxonomic assessments.
Working with the indigenous people of Guyo, researchers attached 60 sets of camera traps to trees in a previously unexplored part of the Leuser ecosystem in Sumatra, Indonesia, one of the largest intact rainforests in Southeast Asia.
The traps captured images of 17 tigers over a 90-day period in 2023 and 18 tigers in 2024, while previous 90-day surveys in Sumatra found an average of only seven tigers. In total, the survey identified 14 adult female tigers, 12 males and three pairs of cubs, as well as one adult tiger of unknown gender.
“It exceeded my expectations only because the literature before this study said we shouldn't have found tigers in that density,” he says. Joe Figel at the Hutan Harimau Conservancy. “So this was a very promising result and shows a lot of the efforts that are going on in this region.”
Sumatran tigers are threatened by poaching for trophies and traditional Chinese medicine, as well as the cutting down of dipterocarp trees, a valuable deciduous species. Due to data limitations, population estimates range from 173 to 883.
Although 90-day periods were used for comparison, the researchers ultimately conducted the study over 180 days in both 2023 and 2024, which provides more reliable data across seasons, says Deborah Martir of the non-governmental organization Flora and Fauna International, which was not involved in the study.
The mother cares for the large male cub, which was spotted living successfully on its own eight months later.
Phil et al. 2025, BKSDA, DLHK
The higher-than-expected number of tigers in the Leuser ecosystem shows that the lowland forests are rich in prey, especially sambar deer, Figel said. It also suggests that monthly walks by rangers are preventing poaching.
Near Gunung Leuser National Park, the study area is patrolled by rangers paid by non-governmental organizations Forum Konservasi Leuser and Hutan Harimau in partnership with the Environment and Forestry Service of the formerly war-torn Aceh region.
But research shows more rangers are needed. In recent years, tigers have gone extinct in Vietnam, Cambodia and Laos.
“What more wake-up call do we need?” says Figel. “The tiger in Southeast Asia is really in dire straits right now.”
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