- A new camera-trapping study in Indonesia’s Aceh province has identified an ample but struggling population of Sumatran tigers, lending fresh urgency to calls from conservationists for greater protection efforts in the critically endangered subspecies’ northernmost stronghold forests.
- The study focused on the Ulu Masen Ecosystem, an expanse of unprotected and little-studied forest connected to the better-known Leuser Ecosystem, the only place on Earth that houses rhinos, tigers, elephants and orangutans.
- The big cat population and its prey likely contend with intense poaching pressure, the study concludes; their forest home is also under threat from development pressure, illegal logging, rampant mining and agricultural encroachment.
- As a key part of the Leuser–Ulu Masen Tiger Conservation Landscape, experts say Ulu Masen merits more conservation focus to protect the tigers, their prey populations and their habitats.
Camera-trap surveys have documented a sizeable but struggling population of Sumatran tigers clinging on in unprotected forests in Indonesia’s Aceh province. The study is the most robust evidence to date of the presence of the critically endangered big cats in the Ulu Masen Ecosystem, a little-studied landscape adjoining Sumatra’s better-known and relatively well-protected Leuser Ecosystem.
Spanning 9,500 square kilometers (nearly 3,700 square miles) of rugged and mountainous terrain at the northwestern tip of the island of Sumatra, the majority of Ulu Masen falls outside Indonesia’s network of protected areas. As such, the biodiverse landscape is rarely considered within national conservation policy and budgeting.
However, Ulu Masen is straining under development pressure, illegal logging and poaching, and in dire need of conservation attention. In addition to Sumatran tigers (Panthera tigris sumatrae), it’s also home to a host of other rare and threatened species. Critically endangered Sumatran elephants (Elephas maximus sumatranus) and Sunda pangolins (Manis javanica) have been recorded in the landscape, alongside other key forest carnivores such as Sunda clouded leopards (Neofelis diardi), marbled cats (Pardofelis marmorata) and dholes (Cuon alpinus), and more than 300 species of birds.
To assess the tiger population, the study team led by Joe Figel, science adviser at the Leuser International Foundation, installed camera traps at 52 locations across Ulu Masen’s vast landscape. Between 2020 and 2022, they amassed 6,732 nights’ worth of recordings, ultimately photographing a total of 11 individual tigers, all of them adults. They published their findings in Scientific Reports.
Figel and his colleagues also documented ample populations of animals that tigers prey on, including sambar deer (Rusa unicolor), serow antelope (Capricornis sumatraensis), wild boar (Sus scrofa) and southern red muntjac deer (Muntiacus muntjak). The widespread presence of prey and extensive forest cover in Ulu Masen “provide favorable conditions to support tiger conservation and recovery,” the authors note. The findings should help government agencies in Aceh to formulate a tiger conservation action plan for the Ulu Masen Ecosystem, they say.
Sumatran tigers are the rarest and most distinct of the tiger subspecies. As few as 400 individuals are thought to remain in the wild. They differ both genetically and physically from the other living tiger subspecies, all of which are native to mainland Asia. Sumatran tigers are typically slightly smaller and darker in color.
Experts say the new evidence of tigers roaming Ulu Masen underscores the urgent need for conservation funders and policymakers to step up protection efforts to safeguard the big cats, their prey and their forest home from impending threats. Increasing the number of rangers patrolling the landscape and scaling up monitoring efforts should be priorities, they say.
“Ulu Masen is part of the Leuser–Ulu Masen Tiger Conservation Landscape, so it is undoubtedly important for tigers and wildlife and should be protected,” Hariyo T. Wibisono, director of conservation NGO SINTAS Indonesia and a member of the Cat Specialist Group at the IUCN, the global wildlife conservation authority, told Mongabay.
A certain ratio
While the tiger observations indicate a “sizeable” population in Ulu Masen, the study notes the demographics could signal deeper problems. Among the 11 tigers identified, eight were adult males, two were of unknown sex, and just one was female. They detected no cubs.
Hariyo, who was not involved in the study, said he wasn’t surprised the camera traps failed to detect cubs, which are “not as active as, and don’t move as far as adults.” However, the “pronounced” male-skewed sex ratio “is indeed alarming and should be of concern,” he said.
For one, the paucity of breeding-age females raises questions about the viability of the Ulu Masen subpopulation. The authors also note that a dominance of males and lack of cubs indicates the population faces heavy poaching pressure.
The threat of poaching extends throughout tigers’ range, even into the remotest corners of Aceh province, according to Rudi Putra, a biologist and chair of the Leuser Conservation Forum. “Tiger skin is still in big demand,” he said. Persistent markets for tiger skins, bones and other body parts used in traditional medicines in China and Vietnam drive poaching and the illegal trade.
Besides direct targeting for the illegal wildlife trade, indiscriminate snaring is an acute threat in Aceh province. Hunters typically set wire snares along wildlife tracks and ridgelines to catch wild boar and ungulates for consumption, but roaming tigers are just as vulnerable to being caught. Indeed, camera traps repeatedly detected a three-legged male in Ulu Masen, “most likely the result of limb loss from snare entrapment,” the study says.
Boosting the number of rangers patrolling forests is a proven way of curbing the snaring crisis, according to the study. A 2015 study in Sumatra’s Kerinci-Seblat National Park, for instance, found ranger patrols could reduce snares by 41%. Figel and his colleagues calculated 560-640 trained rangers would be required to adequately cover Ulu Masen’s vast landscape.
Habitat loss presents another threat. Development pressure, illegal logging and mining, and agricultural encroachment continually erode and fragment Ulu Masen’s unprotected forests. Between 2001 and 2023, 370 km2 (about 140 mi2) of primary forest cover was destroyed in Ulu Masen, representing a 4% loss, according to Figel.
Hariyo said the biggest concern is the forest corridor that connects Ulu Masen to the wider Leuser landscape, which houses roughly 30% of the world’s remaining Sumatran tigers. Preserving the integrity of these wildlife thoroughfares should be a top priority, he said, since they facilitate vital genetic exchange between Leuser’s core breeding tiger population and smaller satellite subpopulations. “Ongoing and potential threats against the natural corridor connecting Ulu Masen and Leuser ecosystem should be of major concern,” Hariyo said.
One such threat is the proliferation of illegal mining, according to Rudi, who has worked on forest connectivity in the Leuser Ecosystem for more than two decades. Although several gold, copper and silver mining concessions are permitted within Ulu Masen, unchecked illicit operations are eating even into conservation areas. “Mining is the biggest driver of fragmentation between Leuser and Ulu Masen,” Rudi told Mongabay.
Data gathered by local civil society groups recently showed 68 km2 (26 mi2) of illegal gold mines have proliferated throughout Aceh, prompting activists to call on authorities to take serious measures against the opaque networks controlling the activity.
A funding gap
While the study authors and experts agree that better protection would improve the outlook for tigers and multiple other species in Ulu Masen, they also acknowledge it will be no simple task.
Ulu Masen is currently categorized as a “provincially strategic area” within Indonesia’s conservation planning system. As such, it’s managed at the provincial rather than national level, and therefore doesn’t receive conservation funding from the central government.
To make matters worse, the provincial agencies responsible for managing Ulu Masen, receive little support from outside funders. While a small group of local and international NGOs have managed community-run ranger patrols and human-wildlife conflict programs in recent years, experts say these efforts are nowhere near the scale of what’s required to protect such a formidable area.
“Most of the critical areas in the Leuser Ecosystem are covered [by wildlife protection teams], but not in Ulu Masen,” Rudi said. “This is the main reason why the [tiger] population in Ulu Masen is declining.”
Rudi said conservation organizations struggle to secure funding to continue their existing work in Leuser, let alone expand their coverage to encompass Ulu Masen. Nonetheless, he said he’s hopeful the new evidence about Ulu Masen’s precarious tiger population will spur more investment and dedicated action from conservation funders. “They can see that there is a crisis,” he said.
Inclusive conservation
Hariyo said multidisciplinary approaches are likely to be the most effective when managing large predators like tigers. Increasing the number of rangers patrolling the landscape is just one part of the solution, he said. It’s also necessary to scale up other surveillance options, such as community wardens, undercover investigation teams, and anti-trafficking networks. Leveraging nature-based solutions while taking account of the views of local communities could also prove fruitful, he added.
“Strictly enforcing laws through ranger patrols in nonprotected areas like Ulu Masen, where most of the forest-edge communities still depend on natural resources, could lead to severe social conflicts,” Hariyo said, adding that “dedicated and robust studies on sociocultural aspects” will be required in addition to further scientific wildlife monitoring.
Indeed, community-led forest protection is gaining traction in Ulu Masen. In October 2023, Indonesia’s Ministry of Environment and Forestry issued legal recognition to 225 km2 (87 mi2) of ancestral forests within the landscape. This effectively granted the eight traditional communities who manage the newly recognized lands the rights to commence plans to maintain their forests sustainably, zoning some parts as protection areas.
While this is a small start, Rudi said he’s confident tiger numbers will rebound in Ulu Masen if they’re afforded large enough areas of habitat free from human threats. “We’ve learnt from Leuser that when we lose tigers from an area, they can recover well since they are cats — every year they can have three or four babies,” he said. “Wildlife management is not difficult if we know that they are still breeding. They just need protection from us.”
Banner image: An adult Sumatran tiger. Image by Rhett A. Butler / Mongabay.
Carolyn Cowan is a staff writer for Mongabay.
Citations:
Figel, J. J., Safriansyah, R., Baabud, S. F., & Hambal, M. (2024). Intact, under-patrolled forests harbor widespread prey but a male-biased tiger population in the Ulu Masen Ecosystem, Sumatra, Indonesia. Scientific Reports, 14(1). doi:10.1038/s41598-024-75503-0
Figel, J. J., Safriansyah, R., Baabud, S. F., & Herman, Z. (2023). Snaring in a stronghold: Poaching and bycatch of critically endangered tigers in northern Sumatra, Indonesia. Biological Conservation, 286, 110274. doi:10.1016/j.biocon.2023.110274
Linkie, M., Martyr, D. J., Harihar, A., Risdianto, D., Nugraha, R. T., Maryati, … Wong, W. (2015). Safeguarding Sumatran tigers: Evaluating effectiveness of law enforcement patrols and local informant networks. Journal of Applied Ecology, 52(4), 851-860. doi:10.1111/1365-2664.12461
See related story:
Where Javan leopards thrive, so do other wildlife, study shows
FEEDBACK: Use this form to send a message to the author of this post. If you want to post a public comment, you can do that at the bottom of the page.
Credits
