Kutai National Park

Rodman (1978) carried out primate surveys in the Kutai National Park (then the Kutai Nature Reserve) in 1970–1971 (1 May 1970 to 31 July 1971) and 1975 (1 July to 24 August). His study site was on the Mentoko River, just south of the Sengata River in the northeast corner of the park (Fig. 1; location2 in Table 1). In the 1971 study, Rodman (1978) recorded seven P. hosei groups (then referred to as P. aygula, following Napier and Napier [1967]) in an area of 2.74 km², estimating a density 2.6 groups/km2. From this, and based on a group size of eight, Rodman calculated a density of 20.4 individuals/km2. Berenstain (1986) reported on the aftermath of forest fires in 1982–1983; fires that destroyed 3.5 million ha of mainly forested land in East Kalimantan. Only one-quarter of the 3 km² forest at Mentoko remained, but there were still six groups of P. hosei there. Azuma (1988) also reported that the species could still be found in Kutai National Park. Fires again ravaged East Kalimantan's forests in 1991/1992 and 1993/1994, and the El Niño-related fires of 1997–1998 destroyed a total of 5.2±0.3 million ha in the region (Siegert et al. 2001). Of this about 2.6 million ha of forest was burned, with varying degrees of damage but primarily affecting recently logged forests. By the time the rains started at the beginning of May 1998 almost the entire basin area in the Kutai district had been burned (Hoffmann et al. 1999; Siegert et al. 2001) and only 5% of the national park remained forested (Meijaard and Nijman 2000). Nijman (2001) failed to locate any P. hosei groups in a survey in the eastern part of the Kutai National Park in 2000.

Table. 1.

Results of the survey for Presbytis hosei canicrus in the 9 localities in the districts of Sangkulirang and Karangan in eastern Borneo: 5 March 2008 to 6 April 2008. Also listed are other primates recorded: slow loris (Nycticebus coucang), long-tailed macaque (Macaca fascicularis), pig-tailed macaque (M. nemestrina), proboscis monkey (Nasalis latvatus), the silvery leaf monkey (Trachypithecus cristatus), Müller's grey gibbon (Hylobates muelleri), and the Bornean orangutan (Pongo pygmaeus).

We surveyed three sites in Kutai National Park (Mentoko, Prefab, Melawan) and conducted a river-boat survey along the Sangata River over 20 days. We were unable to find any evidence that P. hosei could still be found there. In Mentoko the forests were entirely secondary, recovering after the forest fires. They were dominated mostly by species of Macaranga (Euphorbiaceae, and typically pioneer) and shrubs, and showed extensive and frequent clearings. The forests of Prefab and Melawan were also largely destroyed, although small primary forest patches remained, some not entirely burned and some relatively intact. These forest patches still supported other primates such as orangutans, Müller's gibbons, and pigtail macaques (Table 1). Besides the major loss of forest, there was significant disturbance from hunting, as well as forest degradation resulting from mining activities (the biggest coal mining corporation in east Kutai) close to Mentoko. Encroachment, illegal logging, hunting and illegal settlement are serious threats to Kutai National Park's future.

“Berangat” is the local vernacular name of Presbytis hosei, although our interviews showed that they can confuse them with other langur species. People we interviewed in Kabojaya village reported that P. hosei was frequently hunted until the late 1990s. They would hunt them for food and especially bezoar stones or “batu geliga” (intestinal concretions valued for traditional medicine, see Nijman 2004). The price of these stones can reach US$20–30 per gram.

Figure 1.

Survey sites for Presbytis hosei canicrus in the districts of Sangkulirang and Karangan in eastern Borneo.

The Sangata River, a refuge for wildlife since the forest fire (Berenstain 1986), has also been largely devastated. There are many illegal settlements and the riparian forest and mangroves along the Sangata River, from the town of Sangata lama to the mouth, have been converted for fish and shrimp farming and for agriculture. We found five groups of “Bekantan” (Nasalis larvatus) and also, in fields and plantations even, the silvery leaf monkey (Trachypithecus cristatus). Although sparse, vegetation in some areas would appear to still provide sufficient habitat for primates; orangutan nests were found in some places.

Hunting by immigrants that arrived with the logging, oil and coal companies undoubtedly contributed to the rarity of P. hosei in the Kutai region towards the end of the 1990s, but we believe that the massive forest fires of 1997–1998 were the main cause of the extirpation of the species in the areas of Kutai National Park that we surveyed. At 198,629 ha, the park is very large (Tresina et al. 2005) and of course more surveys are needed, and it is possible that P. hosei is still surviving in more remote forest patches.

Sangkulirang and Karangan

These areas are more than 100 km to the northeast of Kutai National Park. The occurrence of Presbytis hosei canicrus there was reported by Supriatna and Wahyono (2000). We were unable to find any forest along the road from Sangata (Kutai National Park) to Sangkulirang bay: the area was dominated by grassland, there is coal mining in the area, and also burgeoning oil palm plantations. Upstream of Sangkulirang River there are two major rivers, the Karangan River and Baai River (also called Pangadan River because it flows through the village of Pangadan). Karst mountains comprise the catchment area of these rivers. We took at least ten days to travel the Baai River (35.67 km), a portion of the Karangan River (27.8 km), and the area in the interior northeast of Gunung Beriun along a logging road belonging to PT. Penambangan logging company.

We found just one group of P. hosei canicrus. It was on the banks of the Baai River (01°15′10.9″N, 117°45′20.3″E), near the village of Pengadan. It was composed of five individuals (four adults and a juvenile). They were predominantly grey on the back and whitish on the ventral surface of the tail, on the abdomen and chest up to the neck, and lower face. Black hairs on the upper part of the cheeks and white hairs from the lower lips to the ears give the appearance of two angled lines of long black and white hairs extending back along the side of the face from the mouth to the ears. Their calls are grunt-like and distinct from other members of the genus Presbytis in the region (P. fredericae and P. rubicunda). Presbytis hosei canicrus was seen in a small patch of mangrove at the river edge. The vegetation included such as Rhizopora apiculata, Nypa sp. and Bruguiera parviflora near the water, and Macaranga sp., Ficus sp., and planted mango trees behind the mangrove. There was widespread clearance for oil palm cultivation in the area, and the group was surrounded by plantations. The chances of survival for the group seemed slim. They would evidently need to travel along the ground to reach other forest patches, and in doing so would be susceptible to dogs or to capture for their bezoar stones.

Deforestation is not limited to the lowlands, and extends to the higher elevations such as Gunung Beriun. There the forests have been replaced by Acacia and Gmelina plantations, and there is legal and illegal logging, and also clear cutting for oil palm plantations. These forests have no protected status, but it is possible that P. hosei still exists in remnant patches there. Hunting is evident in this area judging by the number of pets we found (orangutan, gibbon, macaque, and slow loris) (Table 1). Muarabulan villagers informed us that hunting for bezoar stones occurred in the distant past before they became Moslem, but that now the “stone monkey” (P. hosei) is so very rare that they believed it could no longer be found in the forests there.