Camera traps reveal a thriving Sumatran tiger population in Aceh's Leuser forest

What is the background?

The Sumatran tiger is critically endangered, with fewer than 400 believed to remain in the wild across the island. Sumatran tiger population recovery evidence has been scarce and hard to verify, since the animals are elusive and much of their remaining habitat is remote, unlogged forest that is difficult to survey consistently.

What happened?

A camera-trap survey of the northern Leuser ecosystem in Aceh province identified 27 individual tigers — 14 females, 12 males, and one of unknown sex — plus three separate litters of cubs recorded over a six-month period. Researchers captured 282 clear tiger photographs, a rate nearly three times higher than comparable 90-day surveys at other Sumatran sites.

The survey, published in Frontiers in Conservation Science in December 2025, calculated tiger densities of 1.42 to 2.35 individuals per 100 square kilometres in the surveyed zone — more than double the density previously recorded in the neighbouring Gunung Leuser National Park.

How did it happen?

Researchers scaled up camera coverage over two years: 34 cameras from March to May 2023, 59 cameras from June to December 2023, and 74 cameras from May to November 2024, working in collaboration with Indonesian wildlife and forestry agencies and the Aceh provincial government. Females were photographed an average of 14 times each and males 16 times, a sighting frequency high enough to individually identify most of the population from stripe patterns.

“We documented a robust tiger population, apparently among the healthiest on the island,” said Dr. Joe Figel, the study’s conservation biologist. “For those on the ground, the onus now falls on us to double down and adequately protect them.”

Why does it matter?

High female density and repeated cub litters are the clearest signs conservationists look for that a tiger population is not just surviving but reproducing successfully — a harder bar to clear than simply confirming individual animals are present. Finding density levels double those of an already-protected national park suggests the surrounding Leuser ecosystem, much of which sits outside formal park boundaries, is functioning as genuine tiger habitat and deserves protection status to match.

For a subspecies with a wild population once projected to keep shrinking, evidence of an intact breeding population gives conservation agencies a concrete area to prioritise rather than spreading limited ranger and patrol resources evenly across all remaining fragments of habitat.

What were the key results?

• 27 individual tigers identified: 14 females, 12 males, 1 of unknown sex
• Three litters of cubs recorded over a six-month period
• 282 clear tiger photographs captured, nearly 3x the rate of comparable past surveys
• Camera coverage scaled from 34 to 74 cameras across March 2023–November 2024
• Densities of 1.42–2.35 tigers per 100 km², more than double nearby Gunung Leuser National Park
• Study published in Frontiers in Conservation Science, December 2025
• Survey conducted with Indonesian wildlife and forestry agencies and the Aceh provincial government

What happens next?

Researchers plan to continue camera-trap monitoring in the Leuser ecosystem to track whether the cub litters recorded in 2024 survive to breeding age.

Aceh provincial authorities are expected to weigh the survey’s findings when reviewing protection status for forest areas outside the existing Gunung Leuser National Park boundary.

Conservation biologists said they will publish follow-up density estimates as camera coverage expands to neighbouring, currently unsurveyed sections of the Leuser ecosystem.

World Animal Rescue Network funds anti-poaching patrols, rapid-response teams for human-tiger conflict, and habitat protection across Indonesia and Malaysia, and said sustained ranger presence in newly confirmed habitat like Leuser is exactly where that funding has the most impact. Readers who want to support that frontline work can donate to save a tiger.

Indonesian wildlife agencies said they will continue coordinating anti-poaching patrols with local communities bordering the Leuser ecosystem as the new density data is reviewed.