The Ulu Masen Ecosystem spans 9,500 km² of tropical rainforest in Aceh province. Located about 4 degrees north of the equator, the region is connected to the Leuser Ecosystem and forms part of the immense Sundaland Biodiversity Hotspot. Ulu Masen’s diverse assortment of habitats – montane forest, lowland rainforest, and tropical pine forest – still provide refuge for several dozen tigers.
Since 2019 we have documented – alongside key collaborators from Aceh-based NGOs, government agencies, and universities – a widespread prey base, which is good news for tigers. But we also found demographic characteristics that indicate tigers face heavy poaching pressures. Our most recent findings indicate high population turnover, an unbalanced sex ratio heavily skewed towards males, and a lack of evidence of reproduction. Tiger-targeted protection is urgently needed to ensure the species’ recovery in this undervalued landscape.
The situation in the Leuser Landscape is more stable, for now. Since 2023, we have documented 27 adult tigers in this immense ecosystem, which still contains extensive tracts of hill and lowland forests. Similar to Ulu Masen, however, poaching and hunting – of tigers and their prey – is widespread. With consistent patrolling, we anticipate the tiger populations in Leuser to persist for years to come.
