Presbytis bicolor, Aimi & Bakar, 1992, Aimi & Bakar, 1992

There are 30 records of

P. bicolor View in CoL

from 1977 to 2022 from various localities in Sumatra ( Table 1 View Table 1 ). They were found in three provinces of central Sumatra, including Riau, West Sumatra and Jambi Province ( Fig. 1 View Figure 1 ).

Note of locations in the map:

1. Mentioned as “Batang Kering, West Sumatera ” ( Aimi & Bakar 1992). Batang Kering (0°42'S,100°49') is an area in Kamang Baru Subdistrict, Sijunjung District , West Sumatra Province.

2. Mentioned as “Sungei Kambut, near Kiliranjao (0°53'S, 101°22'E), West Sumatera ”( Aimi & Bakar 1992). The correct spelling of Sungei Kambutis Sungai Kambut. This area is located in Pulau Punjung Subdistrict   GoogleMaps , Dharmasraya District   GoogleMaps , West Sumatra Province.

3. Mentioned as “Batang Kering, near Kiliranjao, West Sumatera ” ( Aimi & Bakar 1992). This location is nearly similar to number 1, located in Kamang Baru Subdistrict, Sijunjung District , West Sumatra Province.

4. Mentioned as “Galagah, near Kiliranjao, West Sumatera ” ( Aimi & Bakar 1992). The correct spelling of Galagah is Galogah (0°46'S, 101°18E). This area is located in Kamang Baru Subdistrict, Sijunjung District   GoogleMaps , West Sumatra Province.

5. Mentioned as “Sungei Tambang, near Kiliranjao, West Sumatera ” ( Aimi & Bakar 1992). The correct spelling of Sunget Tambang is Sungai Tambang (0°51'S, 101°23'E). This area is located in Kamang Baru Subdistrict, Sijunjung District   GoogleMaps , West Sumatra Province.

6. Mentioned as “Parit Rantang, near Kiliranjao, West Sumatera ” ( Aimi & Bakar 1992). Parit Rantang or Kunangan Parit Rantang (0°50'S, 101°22'E). This area is located Kamang Baru Subdistrict, Sijunjung District   GoogleMaps , West Sumatra Province.

7. Mentioned as “Siatang, near Kiliranjao, West Sumatera ” ( Aimi & Bakar 1992). The location could be Sialang or Sialang Baru (0°54'S, 101°26'E), Pulau Punjung Subdistrict, Dharmasraya District   GoogleMaps , West Sumatra Province.

8. Mentioned as “Sungei Lansat, near Kiliranjao, West Sumatera ” ( Aimi & Bakar 1992). The correct spelling of Sungei Lansat is Sungai Lansek (0°54'S, 101°21'E). This area is located Kamang Baru Subdistrict, Sijunjung District   GoogleMaps , West Sumatra Province.

9. Mentioned as “Kamang, near Kiliranjao, West Sumatera ” ( Aimi & Bakar 1992). This area is located in Kamang Baru Subdistrict (0 46' S, 101°19'''E), Sijunjung District , West Sumatra Province.

10. The location is Talang Lakat Village (0°50’S, 102°31’E), near Camp Granit, Bukit Tiga Puluh National Park   GoogleMaps , Riau Province.

11. Reported in Sinjunjung   GoogleMaps , near Sawah Lunto (0°38'S, 101°18'E), West Sumatra Province.

12. Reported in Danau Embat (1°38'S, 103°9''E), Maro Sebo Ilir Subdistrict, Batanghari District , Jambi Province (based on the map in Suhono, 2016).

13. Reported in Sengeti Subdistrict   GoogleMaps (1°28'S, 103°30'E), Muaro Jambi District, Jambi Province. Most of them are found in rubber plantations.

14. Observed in the area between Kiliran Jao (West Sumatra) and Kuantan Singingi District   GoogleMaps (0°53'S, 101°46'E), Riau Province. Found in rubber plantations, with a combination of remaining forest and palm oil plantations.

15. Tanjung Lanjut Village   GoogleMaps (1°23'S, 103°21'E), Sekernan Subdistrict, Muara Jambi District, Jambi Province. Found in rubber plantations, with a combination of remaining forest and palm oil plantations.

16. Near Danau Bangko (1°32'S, 103°20'E), Lubuk Ruso Village, Pemayung Subdistrict, Batanghari District   GoogleMaps , Jambi Province. Found   GoogleMaps in rubber plantations, with a combination of remaining forest and palm oil plantations.

17. Around the highway in Sengeti (1°29'S, 103°30'E), Sekernan Subdistrict, Muaro Jambi District, Jambi Province. Found in rubber plantations, with a combination of remaining forest and palm oil plantations.

18. Observed in Camp Granit (0049 ’S, 102031 ’E), Bukit Tiga Puluh National Park , Riau Province. Found in rubber plantations, with the combination of remaining forest and palm oil plantations.

19. Observed in Lubuk Ruso Village (1°30'S, 103°22'E), Pemayung Subdistrict, Batanghari District   GoogleMaps , Jambi Province. Found   GoogleMaps in rubber plantations, with a combination of remaining forest and palm oil plantations.

20. Observed in Kuap Village 1 (1°30'S, 103°21' E), Pemayung Subdistrict, Batanghari District   GoogleMaps , Jambi Province. Found   GoogleMaps in rubber plantations, with a combination of remaining forest and palm oil plantations.

21. Observed in Kuap Village 2 (1°33'S, 103°18'E), Pemayung Subdistrict, Batanghari District   GoogleMaps , Jambi Province. Found   GoogleMaps in rubber plantation, with a combination of remaining forest and palm oil plantations.

22. Observed in Kuap Village 3 (1°33'S, 103°17’E), Pemayung Subdistrict, Batanghari District   GoogleMaps , Jambi Province. Found   GoogleMaps in rubber plantations, with a combination of remaining forest and palm oil plantations.

23. Tanjung Lanjut Village   GoogleMaps (1°24'S, 103°25'E), Sekernan Subdistrict, Muaro Jambi District, Jambi Province. Found in rubber plantations, with a combination of remaining forest and palm oil plantations.

24. Suko Awin Wijaya Village   GoogleMaps (1°20'S, 103°18'E), Sekernan Subdistrict, Muaro Jambi District, Jambi Province. Found in rubber plantations, with a combination of remaining forest and palm oil plantations.

25. Bukit Baling Village   GoogleMaps 1 (1°23'S, 103°28'E), Sekernan Subdistrict, Muaro Jambi District, Jambi Province. Found in rubber plantations, with a combination of remaining forest and palm oil plantations.

26. Bukit Baling Village   GoogleMaps 2 (1°24'S, 103°29'E), Sekernan Subdistrict, Muaro Jambi District, Jambi Province. Found in rubber plantations, with a combination of remaining forest and palm oil plantations.

27. Anak Talang Village (0°45'S, 102°66’E), Batang Cenaku Subdistrict, Indragiri Hulu District , Riau Province. Found in a rubber plantation.

28. Reported in Bukit Tiga Puluh National Park, collected in 2007-2008. (Meyer 2011, Meyer et al. 2011, 2012). Specimens recorded JF295109, JF295106 and JF295108.

29. Reported in Sengeti, Muaro Jambi District, Jambi Province, collected in 2007-2008 (Meyer 2011, Meyer et al. 2011, 2012), specimens recorded as JF295107.

Distribution and Habitat

The P. bicolor is distributed between the Indragiri River and the Batanghari River of central Sumatra ( Aimi & Bakar 1992; Anandam et al. 2013; Beausejour et al. 2021). All of our records are recorded within this range ( Fig. 1 View Figure 1 and Table 1 View Table 1 ). Based on our observations (localities number 13 to 27 in Fig. 1 View Figure 1 and Table 1 View Table 1 ), the P. bicolor is found in the rubber plantations Hevea brasiliensis ( Euphorbiaceae ) in lowland habitats ( Figs. 4- 5 View Figure 4 View Figure 5 ).

Groves (2001) suggest P. bicolor is a montane form, with three skins reported in the Leiden Museum from north Kerinci by Hooijer (1962), which are variants of this species grading toward P. melalophos . However, north Kerinci is not located between the Indragiri River and Batanghari River, and based photo of Presbytis in Kerinci Mountain ( Beausejour et al. 2021), it is likely refer to P. m. nobilis. Further references reported P. bicolor inhabits highlands or montane forest habitats ( Anandam et al. 2013; Supriatna 2019; Beausejour et al. 2021), but their map for the distribution range of P. bicolor did not reach the highlands zone of Bukit Barisan Mountain range in Sumatra. Based on the available information ( Table 1 View Table 1 ), the highest area where P. bicolor was recorded is the Sijunjung District, which has the highest elevation of this area c. 902 m ( Mapcarta 2022). Whitten et al. (2000) classified the average elevation of the forest zones in Sumatra range 0-1.200 m as lowland habitats. According to Nijman (2021), P. bicolor inhabits lowland and hill forests.

Nijman (2021) summarized some additional localities for P. bicolor , including concession areas of the forest plant industry of Riau Andalan Pulp and Paper or RAPP (Riau Province), Rimbang Baling Wildlife Sanctuary (Riau Province), and Bukit Bungkuk Strict Nature Reserve (Riau province). All of these areas are located in the northern part of Sumatra, across the Indragiri River (between Kampar River and Indragiri River, not Indragiri River and Batanghari River). Further investigation suggests that species recorded in Rimbang Baling Wildlife Sanctuary and Bukit Bungkuk Strict Nature Reserve as P. siamensis ; and species found in Bukit Bungkuk as P. femoralis ( Bugiono 2001; LPPM-IPB 2015; Lathifa et al. 2016; Prayogi & Atmoko 2016; Yasir & Sutrisno 2019). The P. bicolor has been reported to occur in Bukit Dua Belas National Park ( Supriatna 2019; Beausejour et al. 2021), but this still needs further confirmation because the park is located across in southern part of Batanghari River (between the Batanghari River and Musi River). Furthermore, Setiawan (2017) reported three primates ( P. melalophos, Agile Gibbon Hylobates agilis and Siamang Symphalangus syndactylus ) from Bukit Bulan, Bukit Dua Belas National Park, without information for P. bicolor .

Records of P. bicolor in forested areas (Bukit Tiga Puluh National Park, Figs. 6-7 View Figure 6 View Figure 7 ) and various habitats, such as plantations and near urban areas, suggest this primate can survive in disturbed habitats. Supriatna (2019) reported that P. bicolor found in primary forest and secondary hill rainforest, shrub or secondary growth, and plantations, considered this species to be tolerant of habitat changes. In Jambi Province, we found remaining secondary forest and old rubber plantations provide suitable habitats for P. bicolor for feeding and roosting ( Figs. 2 View Figure 2 -11).

The P. bicolor was presumed a forest-dependent species, and the conversion of forests for various purposes (particularly large-scale plantation) have been given impacted on the loss of habitat. Our survey in Jambi Province revealed that this species is tolerant to degraded forest, and also survive in the human-modified habitats, such as rubber plantation or agricultural scale of local people. However, we fail to spot P. bicolor in the Industrial Timber Plantation (locally called Hutan Tanaman Industri or HTI), of the Eucalyptus plantation. It is likely P. bicolor avoided Eucalyptus trees.

Behaviour

The P. bicolor is diurnal, arboreal, moves quadrupedally in trees and lives in groups of between 8 to 12 individuals consisting of both females and males ( Supriatna 2019). Our observation found there are few groups consisting of up to 15 and more than 20 individuals. On a few occasions, we also found single or two individuals, suggesting they usually live in solitary. Like many other primate species, surilis emit loud, conspicuous vocalizations termed loud calls or long-distance calls ( Meyer et al. 2011). Based on our observations, P. bicolor is commonly silent ( Fig. 6 View Figure 6 ), but when their feel disturbance, at least one of them in the group will prepare a voice that we assume as an early alarming call ( Fig. 7 View Figure 7 ). On one occasion, we have observed their response with noisy calls when a drone flew around them.

Diet and Feeding Ecology

The P. bicolor is known to be folivorous or leaf-eating but has also been seen to consume fruit, flowers, seed and some species of small insects ( Anandam et al. 2013; Supriatna 2019; Nijman 2021). Further details of diets are lacking. During field visits, We were observed P. bicolor consuming leaves of Para rubber tree Hevea brasiliensis ( Euphorbiaceae ) and Mango Mangifera sp ( Anacardiaceae ) ( Figs. 8 View Figures 8 and 9 -11). Local people reported that P. bicolor was observed consuming some agricultural plants, including leaf of Cassava Manihot esculenta ( Euphorbiaceae ), the leaf of Chili Capsicum annuum ( Solanaceae ), the young fruit and seed of Para rubber tree, the leaf and fruit of Jengkol Archidendron pauciflorum (Caesalpinioideae) , the fruit of Mangosteen Garcinia mangostana ( Clusiaceae ) and fruit of Psidium guajava ( Myrtaceae ). Even though P. bicolor fed the plants of the local people, but this species reported does not cause severe economic damage, such as Long-tailed macaque Macaca fascicularis and Southern pig-tailed macaque Macaca nemestrina .

Supriatna (2019) reported P. bicolor has been seen on the ground where they access food and water. On one occasion, we observed P. bicolor go down to the ground, possibly searching for suitable food ( Fig 12 View Figure 12 ). Furthermore, we saw this species escaping to avoid disturbance, crossing the road from old palm oil vegetation to dense rubber vegetation ( Fig. 14 View Figure 14 ).

Threats and Conservation Actions

The P. bicolor has been listed in CITES Appendix II and is protected by Indonesian law ( Anandam et al. 2013; Ministry of Forestry and Environment 2018; Nijman 2021). Nijman (2021) assumed this species was targeted for illegal collecting for the pet trade, but our field visits and interview with local people suggest no indications of hunting for this purpose. The P. bicolor is usually found near settlements, but local people explain this species does not give significant disturbances, particularly to their harvested plants, compared to other primates in this area, Long-tailed macaque and Southern pig-tailed macaque. Both primates usually fed on their crops, and also frequently entered the home for searching food.

Based on our field visits, there are three potential threats, including electrical power lines, domestic dogs and roadkill. On 8 December 2021, we observed P. bicolor with some wounds on the body, roosting in a tree near an electrical power line ( Figs. 15 View Figure 15 and 16 -16). We presumed the wounds were caused by an open electrical power line. In the same location, we found a P. bicolor eaten by the Domestic dog Canis familiaris ( Fig. 13 View Figure 13 ). This primate presumed fall and weak from being electrocuted; then attacked and eaten by a Domestic dog. From January to February 2022, local people reported some roadkills of P. bicolor when this species try to cross the street, with at least two accidents in Pemayung District, Jambi Province. Local people reported that when crossing the street, P. bicolor will not aware of the conditions, and they just jump down and across; this differ from other primates, M. fascicularis and M. nemestrina , who are usually able to watch carefully the situation before across the street.

Mortality due to electrocution from power lines and road accidents are among the major direct anthropogenic threats to the survival of primates (Al-Razi et al. 2019). A case from Peninsular Malaysia from 2012 to 2017 reported 27 leaf monkeys, but none for Macaques ( Kasmuri et al. 2020). In addition, Indonesia and Southeast Asia are regions with the most species number of threatened species in the world negatively impacted by dogs Canis familiaris ( Doherty et al. 2017) .

There are four protected areas reported as habitats for P. bicolor , including Rimbang Baling Wildlife Sanctuary (Riau Province), Bukit Bungkuk Strict Nature Reserve (Riau province), Bukit Tiga Puluh National Park (Riau and Jambi Province) and Bukit Dua Belas National Park (Jambi Province) ( Supriatna 2019; Beausejour et al. 2021; Nijman 2021), but only Bukit Tiga Puluh National Park confirmed as habitat for this primate. Recently, more than 15% of Indonesia’s landmass is formally protected, with 527 reserves (wildlife reserves, nature reserves, nature recreation parks, hunting parks and forest parks) and 50 national parks ( Gaveau et al. 2016). Despite these commendable conservation commitments, losses of Indonesia’s lowland old-growth forests, the preferred habitat of most primates, remain critical today. As P. bicolor found in many human-modified habitats and all of them are not protected areas, it is clear Bukit Tiga Puluh National Park as a most important area in the conservation concerns of this species. As proposed by Anandam et al. (2013) and Nijman (2021), further surveys and clarification are needed to assess the distribution and conservation status of P. bicolor . The status of P. bicolor is currently classified as Data Deficient on the IUCN Red List ( Nijman 2021). Further studies and more information will help to determine IUCN Red List status in the future, and will the give best conservation action plans to be taken.