In this snapshot from a camera trap on the Indonesian island of Sumatra, a resident female Sumatran tiger is grooming one of her 2 large male cubs in October 2023. Image via Figel et al./ BKSDA-Aceh/ DLHK/ Frontiers.
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Researchers on the Indonesian island of Sumatra installed infrared camera traps in a multi-year effort to study endangered Sumatran tigers.
They say they found 3 times more endangered Sumatran tigers than previous surveys. In total, the team was able to identify 27 individual tigers from the images.
This success story for Sumatran tigers is likely due to many factors, including increased protection measures and adequate prey for the tigers.
Frontiers published this original story on December 4, 2025. Edits by EarthSky.
Camera traps find 3 times more endangered Sumatran tigers
Tigers don’t roam across Asia as they used to. But on one island in Indonesia, a population of critically endangered Sumatran tigers might have found a habitat that supplies them with enough space, intact forests and prey to thrive and raise their young.
To examine tiger population densities, researchers working alongside local rangers installed infrared cameras in forests outside the national park system. Their work, in collaboration with the government of Aceh province, resulted in almost three times the number of individual tigers identified, in contrast to previous surveys. Dedicated protection efforts are the main reason for tigers’ persistence in this ecosystem, the team said.
Destroyed habitats, poaching and prey depletion have dramatically reduced tiger habitats around the world. Today, tigers occupy just 5 to 10% of their historical habitats. But on the Indonesian island of Sumatra, an important population of critically endangered Sumatran tigers may persevere, a December 3, 2025, Frontiers in Conservation Science study showed.
Using infrared cameras, researchers working on the island have set out to estimate sex-specific population densities and tigers’ movements during three surveys. Lead author Joe Figel is a conservation biologist who works with Indonesian wildlife and forestry agencies. Figel said:
We documented a robust tiger population, apparently among the healthiest on the island. For those on the ground, the onus now falls on us to double down and adequately protect them.
An aerial view of the lowland river valley in the Leuser ecosystem on the island of Sumatra in Indonesia. Image via Joe Figel/ Frontiers.
Long-time tenants
In many ways, the Leuser ecosystem is ideal habitat for Sumatran tigers. Three times the size of Yellowstone National Park, it is the largest contiguous tiger habitat remaining in Sumatra. It’s made up of lowland, hill and montane forests, of which 44% are classified as intact forest landscape. Figel said:
It’s also more thoroughly patrolled by rangers than nearly any other place on the island.
Working with local collaborators from communities at the edges of the study area, the team put up cameras in the northern stretches of Leuser, located in Aceh province, and kept them there for three monitoring periods: 34 cameras were installed during March to May 2023, 59 cameras between June and December 2023, and 74 cameras between May and November of 2024. Figel explained:
Multi-year camera trap monitoring is critically important for estimating key tiger demographic parameters such as survival, recruitment, tenure and population growth rate. With these data – and only with these data – can we even begin to evaluate conservation efforts.
Monitoring the Sumatran tiger
During the monitoring periods, the team captured a total of 282 sufficiently clear images of Sumatran tigers to allow for the identification of individuals. Analyzing stripe patterns, the team identified 27 individuals from camera-trap images, including 14 females, 12 males and one tiger of unknown sex. The relatively high number of tigers suggests there is adequate prey in the area to support tiger presence.
Over the study period, cameras photographed female and male individuals an average of 14 and 16 times, respectively. High densities of female tigers indicate a healthy tiger social system and high-quality habitats, where they can raise about three litters of cubs over a decade.
During the six-month session in 2023, the images documented three different sets of cubs. They also recorded two tiger brothers together as cubs and later individually as adults.
Watch as a tiger mother grooms her cub. Video via Figel et al./ BKSDA-Aceh/ DLHK/ Frontiers.
The Sumatran tiger is thriving
Inside the Leuser ecosystem lies Gunung Leuser Nation Park. However, researchers conducted the present study in forests provincially protected by the Aceh government. In Indonesia, provincially protected forests receive far fewer resources than national parks, which are supported and managed by the central government.
The camera traps placed by Figel and colleagues snapped nearly three times as many tiger images as during previous 90-day surveys at other sites in Sumatra. Plus, the team was able to identify many more individuals than reported in earlier studies. Only three previous surveys – all carried out in protected national parks – documented more than 10 tigers in a single survey. Higher tiger density estimates than reported in the present study were only documented in an intensive protection zone in southern Sumatra.
The current study also provides valuable insights for future monitoring of tigers, the team said. The data on tiger movement collected here could, for example, inform survey protocols and optimal camera spacing.
The high numbers of tiger sightings reported here highlights a success story that is due to a multitude of factors, said the team. Figel said:
Thanks to the work, activities and support of government agencies, local Acehnese and Gayo communities, donors and other researchers, Leuser has maintained important patches of lowland and hill forests where, in Sumatra, tiger prey densities reach their highest levels. The persistence of these habitats and prey populations are the main reasons for our findings.
More camera trap pics
Tiger snapshot from camera trap. Image via Figel et al./ BKSDA-Aceh/ DLHK/ Frontiers.
This camera trap caught a female tiger with a cub. Image via Figel et al./ BKSDA-Aceh/ DLHK/ Frontiers.
Bottom line: Camera traps on the Indonesia island of Sumatra caught three times as many endangered Sumatran tigers as before. The Sumatran tiger is thriving in this region.
Source: Sumatran tiger density estimates in the Leuser Ecosystem, Sumatra, Indonesia
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