- Five of the six nonhuman primate species found in the Indonesia’s Mentawai Islands have traditionally been hunted; traditional beliefs forbid killing the sixth, Kloss’s gibbon, or bilou.
- With widespread deforestation and the erosion of traditional practices that governed hunting behavior, all of the islands’ primates are now endangered or critically endangered.
- Malinggai Uma Tradisional Mentawai, a grassroots, Indigenous-led organization, is working with communities to protect primates within the framework of Indigenous Mentawai customs.
SOUTH SIBERUT, Indonesia — As night falls over the Siberut jungle, a fire crackles inside the Tateburuk clan’s wooden home, or uma. The walls are covered in traditional Mentawai carvings of forest creatures — birds, lizards, monkeys and gibbons — a reminder that the boundary between the outside world and the home is thin.
Damianus Tateburuk, 43, known to everyone as Dami, glances up at the dozens of primate skulls hanging from the doorframe. “They are offerings,” he says. “They cleanse the uma of bad spirits.”
The Mentawai people, Indigenous to the Mentawai Islands off the west coast of Indonesia’s Sumatra Island, are hunters, and the islands’ endemic primates have long been important targets. Five of the six primate species found in the Mentawai Islands are traditionally hunted: the simakobu (pig-tailed langur, Simias concolor), joja pagai (Mentawai langur, Presbytis potenziani), joja siberut (Siberut langur, Presbytis siberu), bokkoi pagai (Pagai Island macaque, Macaca pagensis) and bokkoi siberut (Siberut macaque, Macaca siberu). The only primate traditionally spared is the bilou (Kloss’s gibbon, Hylobates klossii).
“Hunting bilou is forbidden,” Dami says, explaining the role of the bilou as a spiritual messenger in Mentawai belief. “Its songs warn us of bad omens, disasters, and even deaths.”
Growing up, Dami was a prolific hunter. But over time, he noticed that the islands’ primates were becoming harder to find. In 2013, along with his friends Ismael Saumanuk, Vincent Tateburuk and Mattheus Sakaliou, he founded the grassroots organization . Named for an ancestor who Dami says initiated the idea of environmental and cultural preservation, the foundation aims to help protect these animals and their forest.
Mentawai’s endemic primates under pressure
Today, all six of the Mentawai Islands’ endemic primate species are listed as endangered or critically endangered on the IUCN Red List, and their populations are declining fast. A 2020 report estimates that simakobu numbers have dropped by as much as 80-90% over the past 36 years. The bilou, Mentawai’s only ape, has seen a population decline of more than 50% in 45 years, yet it remains one of the least-studied gibbons in the world. “There’s still so little research on the Kloss’s gibbon [bilou], even though it’s one of the rarest species most in need of urgent protection,” says Mariani “Bam” Ramli, founder of the Malaysia-based NGO Gibbon Conservation Society.
Hunting has likely played a role in this decline. A 2014 study estimated that between 4,860 and 9,720 primates were hunted yearly on Siberut Island alone — around 6-22% of the local population.
Traditionally, Mentawai hunting has been guided by strict rules based on animist beliefs, which helped prevent overhunting and protected the bilou. But those beliefs are changing. Research suggests the erosion of Mentawai culture and animist values is weakening the customary laws that once governed hunting behavior.
“Hunting has evolved from being a traditional, subsistence activity using poison-tipped arrows to a more opportunistic activity,” says Rizaldi Rizaldi, a conservation biologist from Andalas University on the Sumatran mainland, who works closely with Mentawai communities to study and protect endemic primates.
Another major threat to Mentawai’s primates is habitat loss. Commercial logging surged in the 1970s, and although parts of Siberut were declared a national park in the 1990s, forest degradation has continued at a worrying pace. Government-issued logging permits, sometimes granted without Indigenous consent, have opened large swaths of forest to commercial exploitation.
Smaller-scale logging, both legal and illegal, is also common, serving as a source of income for local people. “The synergy between logging and hunting is particularly devastating,” Rizaldi says. “Logging not only destroys habitat but also creates pathways into remote areas, making hunting easier and more widespread.”
While not well documented, there have been occasional reports of bilou appearing in the illegal pet trade outside Mentawai. Conservationists warn that even low levels of capture, especially of infants, could further threaten already fragile populations.
Between tradition and survival
In the southern Siberut forest, the air is thick with humidity, and the forest floor is slick with mud. There’s a distant hum of chainsaws coming from various directions at once. Dami veers off the trail, machete in hand, and the others follow through tangled undergrowth. Soon they stop: stacks of freshly cut timber lie on the ground, waiting to be hauled out.
“They usually stop when they hear we’re patrolling,” Vincent says, frowning.
On the way out of the forest, the team encounters two familiar faces: a couple from a nearby village, sitting on a log with a chainsaw by their feet. According to Dami, small-scale illegal logging is driven by demand from Mentawai’s growing surf tourism industry.
“You can get 3 million rupiah [around $180] for 20 pieces of meranti wood. The resorts claim they don’t know where the timber comes from,” Dami says. “But they know.”
Malinggai Uma Tradisional Mentawai now has seven core members. They monitor and support research on primate populations, patrol the forests, remove snares, and raise awareness about primate conservation in local villages.
For them, primates have a deep spiritual significance, especially the bilou. Deeply embedded in Mentawai cosmology, it’s considered the closest animal to humans, and is centrally featured in myths, stories and art. Sikerei, traditional healers with important status in Mentawai communities, invoke bilou in some rituals, imitating their calls and movements through song and dance. The bilou is said to be the “guardian of the forest,” keeping an eye on human activities in the jungle and alerting humans when something is wrong.
Traditional carvings show bilou and other primates in various situations: swinging, eating, defecating. This, Ismael says, symbolizes their role in the forest’s ecology.
“Everything is connected,” he says. “If we don’t have primates, we don’t have the forest, and if there’s no forest, there’s no Mentawai.”
he team takes a longtail boat to Bekkeilu village, where Dami has arranged a meeting with the village chief. It’s their second meeting. During the first, Dami says, he encouraged the chief to speak out against forms of hunting that violate traditional customs. They sit on the wooden porch alongside a few other community members. The villagers haven’t taken this seriously, the chief says. As Dami begins to speak about primate conservation, one man stands up, grabs his rifle, and walks away.
“Why do you care so much about primates?” another man asks. “You didn’t create them.”
Poverty is widespread in the Mentawai Islands, and for many, logging and hunting are seen as matters of survival. This sometimes leads to tension between the Malinggai team and other members of the community.
Not everyone is resistant. “We are slowly changing some people’s minds,” Dami says. As part of its work, the organization currently partners with three village councils, monitoring their primate populations and sharing knowledge through village meetings. It also works with teachers across Mentawai’s 12 public schools to educate children about the theory and practice of forest conservation. Its aim, supported by research, is not to eliminate hunting, which many see as an integral part of Indigenous culture, but to encourage traditional methods: bow and arrow instead of rifles, and ceremonial over opportunistic hunting.
“It’s essential to teach the young generation about the importance of primates and protecting the forest,” Ismael says, adding that youth tend to be more receptive to these ideas. “My children are very interested in conservation,” he says proudly.
Looking ahead for primate conservation
The Malinggai team has long-term goals. Dami says he hopes to designate a protected area on Tateburuk clan land and build a rehabilitation center for rescued local primates. With enough funding, he wants to hire hunters as rangers and educators.
“Hunters know the most about primates,” he says. “And once they have an incentive, we can start to change their mindset.”
Malinggai Uma Tradisional Mentawai is part of a small network of community-based primate conservation efforts in the region, and is distinctive in being entirely Indigenous-led. With limited funding, its work remains precarious, relying mostly on community support and the members’ own dedication. Still, its efforts have attracted partnerships with national and international organizations such as the Gibbon Conservation Society, which lends it technical support and resources.
“Our vision has always been for them to lead the way,” says Ramli from the Gibbon Conservation Society. “This is their home, their forest, and their future.”
Community-led conservation is critical in this context, says Rizaldi from Andalas University. “The idea to conserve should come from them rather than be imposed by the government,” he says.
At the same time, he highlights the need for top-down reforms: “Strengthening forest protection, redesigning land-use plans to include conservation zones, and providing sustainable economic alternatives to logging and oil palm expansion.” Without these changes, he says, “we risk losing not only the primates but also the ecological and cultural integrity of the Mentawai Islands.”
Marcel Quinten, a former primatologist with the German Primate Center, who has led extensive research on Mentawai’s primates, says it’s good practice to “‘convince’ people to stop hunting by providing other means of socio-economic income.” The long-term outlook for some species, he says, may be bleak, but better data are urgently needed to know for sure.
“Now would be the right time to resume our systematic census work from ten years ago and get a good and reliable picture of how density and abundance have changed in time and per species,” Quinten says. If the trends of habitat loss and population decline have continued, he adds, “I’d say at least for Simias concolor [simakobu] and Kloss’s gibbon [bilou], it’s not looking so great.”
Back home, Dami cradles his baby while his 5-year-old daughter playfully swings back and forth on a hammock. The room is scattered with her toys. Above them, a poster of Mentawai’s primates hangs on the wall.
“All I want is for my children to grow up seeing and hearing our primates,” Dami says.
Banner image: Dami Tateburuk, Frengky Sabbattilat, Ismael Saumanuk and Vincent Tateburuk (left to right), take a break during a patrol in Siberut forest. Image by Ana Norman Bermudez for Mongabay.
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Citations:
Quinten, M., Stirling, F., Schwarze, S., Dinata, Y., & Hodges, K. (2014). Knowledge, attitudes and practices of local people on Siberut Island (West-Sumatra, Indonesia) towards primate hunting and conservation. Journal of Threatened Taxa, 6(11), 6389-6398. doi:10.11609/JoTT.o3963.6389-98
Setiawan, A., Simanjuntak, C., Saumanuk, I., Tateburuk, D., Dinata, Y., Liswanto, D., & Rafiastanto, A. (2020). Distribution survey of Kloss’s gibbons (Hylobates klosii) in Mentawai Islands, Indonesia. Biodiversitas Journal of Biological Diversity, 21(5), 2224-2232. doi:10.13057/biodiv/d210551
Whittaker, D. J. (2006). A conservation action plan for the Mentawai primates. Primate Conservation, 20, 95-105. doi:10.1896/0898-6207.20.1.95
Setiawan, A., & Tateburuk, D. (2023). Calling from the wild: Mentawai Gibbon Conservation fieldwork. In S. M. Cheyne, C. Thompson, P.-F. Fan, & H. J. Chatterjee (Eds.), Gibbon Conservation in the Anthropocene (pp. 124–130). Cambridge: Cambridge University Press. doi:10.1017/9781108785402.010
Anas, Y., Rahmahdian, R., Hidayat, A. M., & Djuarni, W. (2024). Characteristics and potential of the extreme poor in the Mentawai Islands Regency, West Sumatra Province. ISAR Journal of Economics and Business Management, 2(5), 7-18. doi:10.5281/zenodo.11407140
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