Kabili Sepilok Forest Reserve

The Kabili Sepilok forest reserve is a Virgin Jungle Reserve (VJR) situated 22 km from Sandakan town along Labuk Road. The main access to the reserve is at the Sepilok Orang-Utan Rehabilitation Centre, where the Mangrove Trail leads to the Sepilok-Laut Mangroves, about 4.5 km south. Others include forest trails from the Rainforest Discovery Centre (RDC). The western and eastern boundaries are accessible as there are unsealed oil palm plantation roads close to the borders.

Latitude/Longitude:   5° 53.174’N-  5° 48.032’N, 117° 54.789’E-118° 0.180’E

The infamous Sepilok Orang-utan Rehabilitation Centre (SORC) is on the northern edge of the VJR. In the north, adjacent to the VJR, is the Taman Botanikal Sepilok FR, where the Forest Research Centre complex and Sepilok Arboretum are situated. The Forest Research Centre (FRC) and the Orang Utan Rehabilitation Centre are administered by the Sabah Forestry Department and the Sabah Wildlife Department, respectively.

The Mangrove Trail stretches about 5.5 km from SORC to the Sepilok-Laut Reception Centre, located in the Sepilok FR (Class VI). Small bridges and bird-watching towers were built and maintained by the SORC management.

Past—In the days of the Chartered Company, William Burgess Pryer, the first British Resident in Sandakan of North Borneo, owned a coffee plantation on the lower Kabili River, in the southwest of the VJR. This plantation was abandoned following an outbreak of disease amongst the labourers and a slump in the coffee trade in 1910. There was another coffee plantation of an unknown owner in the southeastern portion. A graveyard is said to exist on the lower left bank of the Kabili River in Compartment 18. Occasional coffee trees could still be seen in the area in the late 1960s. 

Two of the earliest known logging operations were in 1911 and 1929. Earlier records relating to exploitation and other activities are not available. During the Second World War, the Forest Department personnel stayed inside the VJR.

Low-impact forest exploitation using hand logging followed by heavy machinery such as tractors was conducted in the northeast and most of the southern part of the reserve from 1919 until it was discontinued in 1957. It is estimated that about 24,262 m3 of timber from 670 ha were extracted during that period. In 1948, several hundred hectares of forest in the northern part of the FR were silviculturally treated by the removal of woody climbers and non-productive trees that hampered the regeneration of potentially commercial trees, such as Shorea johorensis, Parashorea tomentella and Eusideroxylon zwageri. The effect of this liberation treatment on the forest stand in this area is unknown. However, the treated forest is structurally comparable to the other old-growth forest in the region. Since 1957, the primary functions of the Kabili-Sepilok VJR have been forestry research and the preservation of some of the major forest types of Sabah.

In 1964, the Game Branch of the Department maintained a station in the north (Compartment 4) to rehabilitate rescued orang-utans. The Branch has since been made into a department by itself, the Wildlife Department and the station came to be known as the Sepilok Orang-utan Rehabilitation Centre.

Creations – Kabili Sepilok forest reserve was gazetted in 1984, covering an area of 4,294 ha. Kabili Sepilok Extension (14 ha) and Kabili Sepilok Extension II (54.6 ha) were subsequently gazetted in 2010 and 2019, respectively. In total, the reserve covers an area of 4,362.6 ha.

Management responsibility – Under Sandakan District Forestry Office. The Wildlife Department manages the SORC and its vicinity. FRC handles all matters of forest research.

Boundary matters – Demarcated.

Management plan – None.

Current Use – Forest ecology and wildlife research, environmental education and nature tourism. There are long-term ecological research plots in the VJR managed and monitored by FRC.

Settlements and other buildings approximately 2 km from the boundary:

• Forest Research Centre (FRC), Sepilok
• Rainforest Discovery Centre
• Bornean Sun Bear Conservation Centre
• Sepilok Orang Utan Rehabilitation Centre
• Sepilok FRC Staff Quarters

Topography

Figure 1: Topography and drainage map of Sepilok Kabili FR

The sandstone ridges give Sepilok its dominant characteristic. These rise rapidly in some cases not far from the mangroves. The hilliest areas are in Compartment 19 and 20, where the Sepilok Trig point (168 m) is located. The southwest corner of the VJR is gently undulating country not exceeding 30 m.

Hydrology

Numerous short rivers, namely Sg. Arang, Sg. Sepilok Besar, Sg. Sepilok Kecil, Sg. Cina, Sg. Pandan, Sg. Pakis, Sg. Suana, Sg. Kabili and Sg. Carib drains to the sea in the south. Sg. Gum Gum drains to the northwest while Sg. Sibuga drains to the northeast.

Soils

Lokan, Maliau, Rumidi, Silabukan, and Weston soil association.

Meteorological data

See Sandakan rainfall data.

Three major forest types have been identified at Kabili-Sepilok VJR, and their distributions co-vary with the distribution of the different soil types and landforms. The lowland dipterocarp forests overlying the soils of the Silabukan and Lokan associations are described here as alluvial and sandstone hill forests, respectively. The forest that overlies the soils of the Maliau association is the heath or kerangas forest.

The alluvial forest is dominated by large dipterocarps reaching a canopy height of 37–45 m or more and > 70 cm in diameter at breast height. In this forest, Parashorea tomentella and Shorea johorensis (both Dipterocarpaceae) are the most abundant canopy species, with Eusideroxylon zwageri (Borneo ironwood, Lauraceae) as large and common middle canopy species. However, these species are totally absent from the sandstone hill forest, where the dipterocarps, i.e. Shorea multiflora, Dipterocarpus acutangulus and Shorea beccariana are the most abundant large trees. The canopy of the sandstone hill forest is about 34–40 m, and occasionally Dipterocarpus acutangulus emerges above canopy height.

The kerangas forest consists of two subtypes; Shorea multiflora/Tristaniopsis subovata (large crown) forest and T. subovata/Garcinia miquelii (small crown) forest. In the former subtype, elements of the sandstone hill tree flora occur on many of the ridges where the most abundant large trees are Shorea multiflora and Ixonanthes reticulata. In the lower-stature kerangas forest, the area is dominated by Tristaniopsis subovata (Myrtaceae).

Flora

A total of 1,285 plant taxa were recorded from the reserve. The ten most speciose families in decreasing order are the Rubiaceae (77), Dipterocarpaceae (75), Fabaceae (72), Phyllanthaceae (61), Annonaceae (59), Meliaceae (55), Lauraceae (53), Euphorbiaceae (50), Moraceae (50) and Malvaceae (48). The dipterocarp diversity in Kabili Sepilok FR is moderately high compared to other forest reserves in Sabah. Of the total taxa, 284 are endemics to Borneo, including 36 endemics to Sabah.

Threatened species under IUCN Red List:

• • 74 Species

Taxa under Wildlife Conservation Enactment 1997: –

Schedule 2, part II – (i) 41 Orchid (ii) 12 Ginger (iii) 2 agarwood (iv) 6 Ramin

Species listed under Appendix II CITES: 

• •  50 Species

Prohibited Species Under Sabah Forest Enactment 1968: 

• • 95 species (mostly of fruits trees and threatened tree species)

One high conservation value plant species, namely Aquilaria malaccensis, is selected as part of the key conservation targets for monitoring biodiversity integrity in Kabili Sepilok FR.

Avian

A total of 197 species belonging to 56 families were recorded. The four most species families are Picidae (16), Nectariniidae, Pycnonotidae, and Alcedinidae. Of the total species recorded, one species was listed as Critically Endangered, two Endangered and nine Vulnerable.

The VJR is an excellent site for bird-watching. Most sought-after bird species in the reserve are Bornean Bristlehead, Black-crowned Pitta, Bornean Necklaced Partridge, Bornean Banded Pitta & Chestnut-collared Kingfisher

Insect

Below are some of the selected and interesting insect species found in the reserve.

• • Butterfly – Iconic species: Troides helena and Troides amphrysus
  • Moth – Iconic species: Attacus atlas and Antheraea helferi
  • Beetle – Iconic species: Chalcosoma moellenkampi (Endemic) and Prosopocoilus occipitalis
  • Damselfly –  Endemic: Rhinagrion elopurae
  • Stick insects – Endemic: Haaniella echinata, Phobaeticus kirbyi and Calvisia marmorata.

Mammals

A total of 13 mammal species from xx families were recorded from this FR.

• • Viverra tangalunga (LC)**
  • Hemigalus derbyanus (NT)**
  • Paradoxurus hermaphroditus (LC)**
  • Mydaus javanensis (LC)**
  • Sus barbatus (VU)*** 
  • Tragulus napu (LC)***
  • Tragulus kanchil (LC)***
  • Macaca nemestrina (VU)**
  • Callosciurus prevostii (LC)
  • Ratufa affinis (NT)**
  • Callosciurus notatus (LC)
  • Pongo pygmaeus (CR)
  • Nasalis larvatus (EN)

Wildlife Conservation Enactment 1997: Schedule 1*; Schedule 2**; Schedule 3***

Research on the forests of this VJR is extensive. Below is some information on historical research activities.

• In 1931, a valuation survey was conducted to determine the growing stock. It was a disappointing figure of 452 cubic feet per acre.
• In 1932, 58 seedlings of mora, Chlorophora tinctoria, from Trinidad were planted in Compartments 15 and 18 on the left bank of the Kabili River. In October, almost 2,000 seeds of belian were line-planted in Compartment 15. The seeds were collected from Sg. Kretam Besar.
• In 1934, Regeneration Improvement Felling was carried out in Compartment 15. The southern half of Compartment 15 was cleared and planted with Liberian coffee in 1894. The mora seedlings planted in 1932 survived. About 500 penaga seeds were planted.
• In 1935, 3 sample plots were established in Compartment 4, 15 and 18. Regeneration improvement felling was carried out in Compartment 14, 15 and 18. Merbau seedlings were planted in Compartment 15. Seedlings of keruing (not specified which), yemane and penaga were planted in Compartment 18. Rotan saga was planted in both Compartment 15 and 18.
• In 1936, Regeneration Improvement Felling was carried out in Compartments 16 and 18. In Compartment 15, seedlings of belian, merbau, majau, penaga (along rivers), kayu cina and kayu chendana were planted. In Compartment 18, tengkawang, rotan saga (from Banjarmasin, Indonesia) were planted. Limpaga was planted in Compartment 4. Wild boars and elephants posed numerous problems to the planting experiments. A linear (Dipterocarp) plot along the path in Compartment 14 was established.
• In 1937, cendana, kayu cina, merbau and rotan saga were planted in Compartment 15. Limpaga, pine, and merbau were planted in compartments 4, 7 and 18 respectively.
• In 1938, Regeneration Improvement Felling (CG 2) were conducted in Compartment 14 and 18. Logging was carried out by NB Trading Co. Ltd. from April to December. Agathis alba (menghilan) and Dacrydium sp. (tempilas) from the Sinsuron River were planted. Wild boars, buffalos, elephants and porcupines posed problems to research activities, especially planting experiments.
• In 1939, Regeneration Improvement Felling were conducted in Compartments 13, 16 and 18. Harvesting was carried out in Compartment 14, 15.
• In 1940, Regeneration Improvement Felling (CG2 & CG1) were conducted in Compartment 13.
• In 1948, Melaleuca leucadendron was planted.
• In 1949, Selective Improvement Felling, for the benefit of the established young stock, were carried out in Compartments 13, 14 and 15. This included climber cutting, felling of Ficus-bound trees and removal of unwanted trees by poison girdling. Small-scale planting of balsa (Ochroma lagopus) (seeds obtained locally) and Melaleuca leucadendron (seeds from Hongkong). Only 79 out of 177 transplants of balsa  survived, and 295 out of 584 transplants of Melaleuca leucadendron.
• In 1950, plantings of Cola acuminata, the African cola nut, were conducted on a small scale. Seedlings were seriuosly damaged. The seeds were obtained from Sapong Estate from trees planted there since the early 1900s. Germination for balsa was poor and transplants were damaged by deer. Melaleuca leucadendron, planted in 1948, continued to flourish despite trampling damage by tembadau. Average height after two years was 10 feet.
• In 1955, a half acre plot of Dipterocarps, mainly Shorea argentifolia, along the path in Compartment 15 was established.
• Three 10-acre (approximately 4 ha) plots were established by JED Fox in the Kabili-Sepilok VJR in June 1968.
• Comparison of insect assemblages (butterfly, dragonfly, and moth) in different lowland forest types in Sabah, Malaysia by Universiti Malaysia Sabah in 2019.

Most of the Department’s research records were lost during the Japanese Occupation and the fire of 1961.

More recent research work:

• In 2000, a multi-disciplinary research project, Biotic Interactions in Tropical Rain Forests (BITRF), began. It was headed by Aberdeen Univeristy, Scotland, with other principal investigators from various universities in the United Kingdom. One of the major sources of funding was from the British Ecological Society. Reuben Nilus, Ecologist at the Forest Research Centre, was the main local collaborator for this project. About five PhD students were involved. Dr Collin Maycock supervised and coordinated field research work. He also carried out studies on the dispersal of dipterocarp fruits. The main project ended in 2003 but smaller studies continue to be carried out. Reuben Nilus’ PhD research was on the effect of edaphic variation on forest structure, dynamics, diversity and regeneration in Kabili-Sepilok VJR.
• The Ecology Section of the Forest Research Centre has permanent sample plots within the Kabili-Sepilok VJR over different soil types, i.e. alluvium, sandstone ridge and kerangas.
• A two-year doctoral research on the activity and habitat use of Lesser Mouse-deer (Tragulus javanicus) was carried out in 1998-2001 by Hisashi Matsubayashi from Tokyo Institute of Technology. The muse-deer was thought to be a nocturnal animal. However, this study showed that individuals forage mainly during the day. Another finding suggests that mouse-deer use food resources in forest gap areas.
• The Kabili-Sepilok FR was one of the sites for a 3-year doctoral research by Carsten A. Bruhl, on the effects of tropical rainforest fragmentation on the leaf litter ant community. The other sites were Kebun Cina Forest Park (Sandakan) and Danum Valley Forest Reserve.

Fire — The risk of fires occurring near the western, northern and eastern boundaries is high during prolonged droughts. Fires are usually started by landowners clearing their lands. During high fire risk periods, Sandakan district forestry office staff and the nearby Forest Research Centre monitor the boundaries daily to look out for fires and advise landowners against using fire to clear their lands.

Encroachment — No encroachment was reported for the last two decades are relatively safe from illegal logging activities. The last report of illegal logging was in the southwest in 2000 and 2001, affecting old research plots. Logs were presumably transported out of the VJR from the mangroves. Occasionally, evidence of hunting of small mammals within the VJRs was observed.

The biodiversity and various forest types, along with the supporting research and nature educational facilities, namely the Rainforest Discovery Centre, Sepilok Orangutan Rehabilitation Centre and Borneo Sun Bear Conservation Centre, make this VJR a central educational and tourism area.