Camera trap photo of a Sumatran tiger in the Leuser ecosystem, Indonesia
Figel et al. 2025, BKSDA-Aceh, DLHK
A camera trap survey has identified more than double the number of critically endangered Sumatran tigers than studies have found elsewhere on the Indonesian island, in a positive sign for protection efforts.
Sumatran tigers are the last remaining population of the subspecies Panthera tigris sondaica, one of two tiger subspecies according to recent taxonomic assessments.
Working with the Gayo Indigenous people, researchers attached 60 sets of camera traps to trees in a previously unstudied part of the Leuser ecosystem in Sumatra, Indonesia, one of the largest intact rainforests in South-East 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 on Sumatra spotted only seven tigers on average. In total, the survey identified 14 adult female tigers, 12 males and three sets of cubs, as well as one adult tiger of unknown sex.
“It surpassed my expectations, just because the literature up until this study said that we weren’t supposed to find tigers in these densities,” says Joe Figel at the conservation organisation Hutan Harimau. “So it was a very promising result, testament to a lot of efforts that have been going on in that region.”
Sumatran tigers are threatened by poaching for trophies and traditional Chinese medicine, as well as logging for dipterocarp trees, a valuable hardwood. Because of limited data, the population estimate varies from 173 to 883.
While the 90-day periods were used for comparison, the researchers ultimately surveyed for 180 days in both 2023 and 2024, which provides a more reliable record across seasons, says Deborah Martyr at the NGO Flora and Fauna International, who was not involved in the study.
A mother grooming a large male cub, who was spotted successfully living on his own eight months later
Figel et al. 2025, BKSDA-Aceh, DLHK
The higher-than-expected tiger count in the Leuser ecosystem shows the lowland forests there are rich in prey, especially sambar deer, says Figel. It also suggests monthly rounds made by rangers have deterred poaching.
Near Gunung Leuser National Park, the study area is patrolled by rangers paid by the NGOs Forum Konservasi Leuser and Hutan Harimau, in partnership with the Environment and Forestry Service of the previously war-torn Aceh region.
But research suggests more rangers are necessary. In recent years, tigers have gone extinct in Vietnam, Cambodia and Laos.
“What more of a wake-up call do we need?” says Figel. “The tiger in South-East Asia right now is really in dire straits.”
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