All four Siberut primates seen in our exploration. Fom left to right: bilou, simakobu, bokoi, and joja.

written by : Imam Taufiqurrahman

With a ‘clean sweep’ of all four Siberut primates, my 11 days journey with Heru Fitriyadi to Siberut Island, Mentawai Islands, West Sumatra, is so astonishing. Joja the Siberut Langur and simakobu Pig-tailed Langur, seen in Southwest Siberut. In South Siberut, we saw bilou Kloss’s Gibbon. While in North Siberut, all four of them, include bokoi or Siberut Macaque, the hardest one.

To complete, a group of Long-tailed Macaque and five other mammals sum up to total of at least 9 mammal species in our list: Spinner Dolphin, Siberut Flying Squirrel, Mentawai Squirrel, Intermediate Roundleaf Bat and some difficult taxa: rats.
For birds, of course, 72 species we saw is so overwhelming. Three of them became my lifer: Ruddy Kingfisher, Storm’s Stork and the Critically Endangered Silvery Wood Pigeon. I don’t know how many lifers Heru has.This journey was actually a combination of duty, cultural experience, and wildlife watching—with a big of luck by some coincidental situations. From 10th-20th February 2026, we spent 2 days in Southwest Siberut, 5 days in South Siberut and 4 days in North Siberut.

As part of the duty, we were asked to speak in a workshop on wildlife ecotourism in Southwest Siberut, facilitated by SwaraOwa. And as the workshop only held for two days, we had plans to continue to visit Siberut NP in the north. This actually may only need about a 5-7 days trip. But, it spanned up to 11 days in total.

Southwest Siberut

In less than an hour after the Mentawai Fast on board, two mammals were seen. The first was a group of Long-tailed Macaque, foraging along the estuary. Seeing them is a bonus, as we were not expecting to see it, just kind of a welcome drink. While in the open sea, a couple groups of dolphins. We only able to take a poor documentation of a group of Spinner Dolphin, as the ferry’s speed did not allowed us to got a good moment.

However, I am quite confident for the dolphin’s id, as they have a quite long rostrum. But, any other suggestions are welcome. A study published in recently reveals the open sea around Padang and Mentawai Islands as a cetacean hotspot, where they found 10 species. Well, that’s almost 1/3 of cetacean species recorded in Indonesia! Surely very potential to develop a whale watching spot.

While for the birds, mostly seabirds seen. We saw at least White-winged, Black-naped and Bridled Tern that confidently id in clear. In one of the small islands off Padang, Heru pointed out a White-bellied Sea-Eagle soaring.
After six hours on board, Mas Yoyok, our local team, picked us up in Maileppet, South Siberut. Soon after, we met our other team members and local partners. Seven of us took a pompong boat to Toloulaggo, Southwest Siberut, where the workshop will be held on the next day.

SwaraOwa has initiated wildlife watching, primarily primate and bird watching, and conservation activities in the subvillage since 2016. This workshop will mark a decade of the initiative and hopefully can bring the wildlife watching ecotourism in the subvillage to the next step.To scale up the initiative, more broader communities are involved, up to village level. Through this workshop, we facilitated a discussion forum for the local communities. To hear their thoughts, ideas and plans about what’s best.

To get to the subvillage, we were passing through the Monaci Canal—named after Italian priest, Ottorino Monaci, who initiated the construction of the canal during six years (1985-1991). This 1.5 kilometers waterway is a monumental work that cuts the long and dangerous route through the open sea. Safe and efficient. For us, there’s another advantage. Thanks to the priest and its students, this mangroves surrounding the canal enabled us to birding along. A Copper-throated Sunbird, Greater Coucal, Ruddy and Stork-billed Kingfisher are among the highlights.

At night in Toloulaggo, we spotlighted through the plantation to look for the Mentawai Flying Squirrel. We saw two individuals. No sighting of Mentawai Scops-owl, despite some birds being already heard so close.

The dawn chorus of bilou enliven the morning. But, we had no sufficient time to look for it as the workshop opened in the morning. We only took our short morning time by boat to look for joja along the beach and found a group feeding at a tree close to the cliff. We watched them from a quite distance, resulting in not a good image. But, still a great experience we had.

The workshop was held in success, with the villagers deciding to take the opportunity in developing the wildlife tourism in their village. They agreed to form a community-based tourism organization. The chief village, the chief of sub-villages, religious leaders, traditional figures, headmaster, and young people attended the workshop and discussed the potential of wildlife ecotourism. Full report of the workshop written by mas Yoyok (in Bahasa), can be read here https://swaraowa.blogspot.com/2026/03/memperkuat-akar-konservasi-workshop.html.

The rain fell right after the workshop ended. Even heavier until night. We waited, but then decided not to go out. The heavy rain also happened in North Siberut and became a catastrophe, as you can read it later. The next morning was promising. We went on trails for wildlife watching. Ismael that walked in front said saw bilou. But, not our luck. We then splitted up. Ismael led four of us to a more deep forest, while the other group led by Vincen followed the trail to our shelter. Just about a couple of minutes later, Ismael signed us something. Turned out, a simakobu sitting nicely. Just only about 10 meters! We had this long face to face moment. The infant joined, until the group went away. It was breathtaking.

On our way to catched up the other group, calls of bokoi were heard. But, we didn’t have more time to spend. With two primates seen and the other two heard, the village surely has a big potention. All of the four Siberut primates—with their simple, but really cool names—joja, bokoi, simakobu and bilou are there! We leave the village in the afternoon, with hope the community-based tourism can be grown.

South Siberut

Actually, we were intended to stay in South Siberut for two days. But, turned out spanned until two more nights. During the first two days, we decided to visit one of our survey area. Mas Yoyok told us about the chance for bilou there. We didn’t wait. On the next day, we visited the forest. But, unsuccess. We spent the afternoon by birding along the estuary to join the Asian Waterbird Cencus. Ruddy Turnstone, Terek and Common Sandpiper, Greater Sandplover and Pacific Golden Plover gathered in flock are some that we saw.

The settlements around the estuary were filled with numerous swiftlet houses. As I remembered, the house was still one or two. Well, surely this ancient commodity are still promising. The next day to the cave. It called Roiget-roiget, means bat. The cave is still sacred to the locals. Pak Darius who led us to the place performed a ritual and sang to the holy spirit asked for permission.

The cave is big, with a huge entrance. It formed not horizontal nor vertical, but diagonal, with about 30° angle in slope. We tried to be very careful walked down the cave. The good thing is, the floor is not slippery. We encountered numerous bats, but only one species found, the Intermediate Roundleaf Bat. While taking pictures, a small mouse is seen crawling. It’s a small brown mouse, with a long tail (1:1.5) proportion of its body. As our knowledge is far from good about rodents, so any suggested ID is very welcome.

The cave explored less than two hours and we were not deep enough actually. I wish I could explore it more, but me and mas Yoyok had a meeting scheduled already and then continued our journey to Padang. We did not anticipate that our plan was close to two national holidays: Chinese Newyear and also beginning of Ramadhan. Many people plan the same to go back to Padang. As a result, the fast ferry was fully booked and we didn’t get tickets. We decided to stay in Muntei village and took the afternoon for a cultural session. We visited the traditional house of Mentawai, uma. Skull of hunted animals—mostly the primates and also wild boars. Mas Yoyok introduced us to Aman Kesi, his relative who became our interpreteur.

We took a house tour and Aman Kesi explained uma with details. For example, he said, if the skulls are facing outside, it means the animals were taken from the wild. But in the opposite, if they facing inside the house, wild boars in particular, that’s from livestock. The skulls are not just a house decoration. It is a status symbol for the family or clan owner. It’s a pride and means a lot to Mentawai people.
I wonder, how many primates were killed along three millennials of the Mentawai people existence?
Study by Whitten & Whitten from eight umas in 1980, resulting in almost 2,400 skulls found. Simakobu is the majority and bokoi holds 25% of total kills. Bilou tends to be the lowest. Aman Kesi said, bokoi is the easiest target, as they have big meat and are slow. That’s almost 50 years ago and hunting is still ongoing. No wonder the primates are so sensitive and shy.

A kailaba puppet hanging in front of the house. For the Mentawai people, they believe that the bird, Oriental Pied Hornbill, is the spirit’s toy. Hanging the puppet in the house can make the good spirit stay. On the next day, we were back to the survey area and this second try was fruitfull. After three and a half hours exploring, we finally saw a group! We experienced ourselves that bilou, the gibbon, can be so silent.

On our last night in South Siberut, we took a chance to look for Mentawai Scops-owl, resulting great success!

North Siberut

Covering almost half of the island, Siberut NP, I must say that the park is one of the mysterious ones. Almost nothing was heard about the park, as a consequence of a long tenurian conflict and rejection. It made the park seem sealed from the outside world. Just last year when SwaraOwa invited the park to share their potential on wildlife—especially primate—watching tourism and invited us to come. They shared their potential and it was so tempting. Here I am now, wanting to prove and experience it by myself. Due to no area in the park for tourism, visit to the park need a special permit called simaksi, a conservation area entry permit. Thanks to Pak Ridho, the head of management area who managed to take care of us and facilitated our visit.

As we were in Southwest Siberut, heavy and long rain also happened in the north. And it was so destructive. The river was flooded and crushed the wooden bridge that connected the villages. That made our journey to the park solely dependent on pompong—for five hours, in rain!

We were the first that came to Bekemen after the flood. The last two hours, where the river intersection and became smaller. Six times we faced an obstacle. Fallen trees and we need to ripe them out from the river. It was dark when we finally came to Bekemen research station. Again, not anticipated or even know that the research station was also affected by the floods. More than 1 meter of water, leave a thick mud inside the shelter. The generator was drowned and dead and the water tank gone.
My imagination for having a hot coffee after being cold by rain for 5 hours soon after arriving was gone. We warmed up ourselves by working out to clean up the mud inside the house. Luckily, the stove is still dry and can be used and we also prepared to brought our dinner.

The next morning, we explored the track. It was hilly, and not an easy trail. The level is more medium to difficult. We saw Simakobu, then a very close call of bokoi. But, just a glimpse without any chance to take a picture. Only Bilou can be photographed as they crosses our path in quick move, but silent.

Three nights as in our first plan, turned out to be just one night. After we had our lunch, we decided to go back. Along the river, we saw at least four groups of Joja. Not as first came, this time they allowed us to be photographed.

Ended up our boat journey in the estuary, we encountered a Storm’s Stork perched in a mangroves. The bird was sitting a couple of minutes. Just perfect!

For two days, we explored the town, rural areas and plantation. Hope to get a chance for another Bokoi. Joja is good to see here. We spent the nights in the park’s mess close in Muara Sikabaluan. The area is close to the beach, with a swamp as the back. Early in the morning, we saw Yellow and Black Bittern. The first was not in the island list. No photographed unfortunately. At night, we spotlighted the rurals and plantations. As dark came, Mentawai Squirrels were still active. Heru even saw the pair mating! I think it was not a common behaviour for this diurnal.

The last morning, Bokoi again soo close, but failed to see it. However, the ferry had a troubled engine. We need to wait until the next morning. Our for the Critically Endangered Silvery Pigeon. We saw them perched high at an emergent tree in the swamp forest. Heru, who tried to approached, saw that the birds feed on a fruiting tree.

There were 10 birds sitting on the emergent tree, with six others seen by Heru feeding on a fruiting tree. A red oval shaped fruit. It called sosoken by the villagers. I was so thrilled with the bird and we thought that was our sweet closing. But it was not. The Mentawai Fast that made us—again—waited, turned out, it was our luck. In the afternoon we went back to the swamp forest and saw two of them posed perfectly.

We finally got a good view and some good pictures of this beautiful and charming monkey. Now that was the closing to our exploration. A very sweet one.

Mammal list
1. Long-tailed Macaque Macaca fascicularis
2. Siberut Macaque Macaca siberu
3. Pig-tailed Langur Simias concolor
4. Siberut Langur Presbytis siberu
5. Kloss’s Gibbon Hylobates klossii
6. Siberut Flying Squirrel Petinomys lugens
7. Mentawai Squirrel Callosciurus melanogaster
8. Intermediate Roundleaf Bat Hipposideros larvatus
9. Spinner Dolphin Stenella longirostris
Unidentified
10. Unidentified rat-1 (cave, S Siberut)
11. Unidentified rat-2 (banana, N Siberut)
12. Unidentified rat-3 (road kill, N Siberut)

Bird list

1. Greater Coucal Centropus sinensis
2. Mentawai Malkoha Phaenicophaeus oeneicaudus
3. Asian Koel Eudynamys scolopaceus
4. Barusan Cuckoo-Dove Macropygia modiglianii
5. Silvery Pigeon Columba argentina
6. Pink-necked Green Pigeon Treron vernans
7. Thick-billed Green Pigeon Treron curvirostra
8. Green Imperial Pigeon Ducula aenea
9. Pacific Golden Plover Pluvialis fulva
10. Tibetan Sand Plover Anarhynchus atrifrons
11. Greater Sand Plover Anarhynchus leschenaultii
12. Terek Sandpiper Xenus cinereus
13. Common Sandpiper Actitis hypoleucos
14. Common Redshank Tringa totanus
15. Ruddy Turnstone Arenaria interpres
16. Red-necked Stint Calidris ruficollis
17. Bridled Tern Onychoprion anaethetus
18. White-winged Tern Chlidonias leucopterus
19. Black-naped Tern Sterna sumatrana
20. White-tailed Tropicbird Phaethon lepturus
21. Storm’s Stork Ciconia stormi
22. Black Bittern Botaurus flavicollis
23. Yellow Bittern Botaurus sinensis
24. Pacific Reef Heron Egretta sacra
25. Little Heron Butorides atricapilla
26. Great Egret Ardea alba
27. Purple Heron Ardea purpurea
28. Grey-rumped Treeswift Hemiprocne longipennis
29. Glossy Swiftlet Collocalia esculenta
30. Edible-nest Swiftlet Aerodramus fuciphagus
31. Mentawai Scops Owl Otus mentawi
32. Crested Honey Buzzard Pernis ptilorhynchus
33. Crested Serpent Eagle Spilornis cheela
34. Blyth’s Hawk-Eagle Nisaetus alboniger
35. Brahminy Kite Haliastur indus
36. White-bellied Sea Eagle Icthyophaga leucogaster
37. Oriental Pied Hornbill Anthracoceros albirostris
38. Blue-tailed Bee-eater Merops philippinus
39. Blue-eared Kingfisher Alcedo meninting
40. Common Kingfisher Alcedo atthis
41. Rufous-backed Dwarf Kingfisher Ceyx rufidorsa
42. Stork-billed Kingfisher Pelargopsis capensis
43. Ruddy Kingfisher Halcyon coromanda
44. White-throated Kingfisher Halcyon smyrnensis
45. Blue-rumped Parrot Psittinus cyanurus
46. Blue-crowned Hanging Parrot Loriculus galgulus
47. Green Broadbill Calyptomena viridis
48. Black-naped Oriole Oriolus chinensis
49. Sumatran Drongo Dicrurus sumatranus
50. Ashy Drongo Dicrurus leucophaeus
51. Black-naped Monarch Hypothymis azurea
52. Tiger Shrike Lanius tigrinus
53. Sunda Crow Corvus enca
54. Ashy Tailorbird Orthotomus ruficeps
55. Pacific Swallow Hirundo javanica
56. Black-headed Bulbul Microtarsus melanocephalos
57. Olive-winged Bulbul Pycnonotus plumosus
58. Common Hill Myna Gracula religiosa
59. Orange-bellied Flowerpecker Dicaeum trigonostigma
60. Scarlet-backed Flowerpecker Dicaeum cruentatum
61. Little Spiderhunter Arachnothera longirostra
62. Yellow-eared Spiderhunter Arachnothera chrysogenys
63. Brown-throated Sunbird Anthreptes malacensis
64. Van Hasselt’s Sunbird Leptocoma brasiliana
65. Copper-throated Sunbird Leptocoma calcostetha
66. Crimson Sunbird Aethopyga siparaja
67. Asian Fairy-bluebird Irena puella
68. Scaly-breasted Munia Lonchura punctulata
69. White-headed Munia Lonchura maja
70. Eurasian Tree Sparrow Passer montanus
71. Forest Wagtail Dendronanthus indicus
72. Grey Wagtail Motacilla cinerea