(I) Physical CharacteristicsThe Kabili-Sepilok Forest Reserve (commonly known as Sepilok) derived its name from two rivers draining into Sandakan Bay. The area is mostly flat, alluvial and slightly undulating. Sandstone ridges are a dominant feature of the forest reserve. There are no large rivers in the area. Drainage to the south, into the Sandakan Bay, is by the Sungai Kabili, Sungai Pakis, Sungai Pandan, Sungai Cina, Sungai Sepilok Kecil, Sungai Sepilok Besar and Sungai Arang. The upper tributaries of the Kabili and Sepilok Besar have their sources within privately-owned, cultivated land, while the other rivers have their entire catchments within the reserve. Drainage from from the north side of the reserve is into Sungai Gum Gum Besar. On the eastern side, drainage is into Sungai Seguntong via Sungai Matalau and several small streams including Masbud, Buaya, Simpang Dua and Simpang Tiga (Payne, 1988).Most of the reserve has classified as the Sandakan Formation consisting mainly of sanstones and mudstones which has been estimated to be upper Miocene or younger in age. Fine to medium-grained sandstone, pale yellow, orange or greyish in colour, predominates in the higher, dissected ridges, while brown or grey mudstones predominate in the intervening lower land of more moderate terrain (Payne, 1988). Four soil associations are recognised within the reserve. Red-yellow podzols occur on the sandstone ridge crests while the sandy lithosols occur on the steep slopes. Extensive podzols are developed on the west. Soils on low mudstone and sandstone hills and alluvial flats occur elsewhere, away from the coastal swamps. Coastal swamp soils are periodically inundated with saline water (Payne, 1988). (II) Climatic ConditionsHeavy rains from the north-east in December and January, rainfall largely influenced by the north-east winds, which generally falls between November and mid-February. The total annual rainfall is about 3,000 mm. Mean daily temperature is 30oC (DWNP, 1987).
Over 200 species of birds have been recorded in the area including several globally endangered species (Payne, 1988). The Kabili-Sepilok Forest Reserve is broadly typical of the lowlands of eastern Sabah. The area is also important for biome and extreme lowland species. The Near Threatened Oriental Darter Anhinga melanogaster has been recorded in the forest reserves (Sheldon et al., 2001).
Non-bird biodiversity: Over 90 species of mammals have been recorded in Sepilok Forest Reserve (Payne, 1988, Matsubayashi et al., 2003). The Asian Elephant Elephas maximus, Sumatran Rhinoceros Dicerorhinus sumatrensis and Tembadau (Bos javanicus) are absent in the reserve but old records showed that they were once found in the area. There is little information on the reptiles, amphibians and freshwater fishes of Sepilok. At least two species of freshwater fishes known only from small streams in eastern Sabah, Acanthophthalmus sandakanensis and Mastacembelus keithi occur within the reserve. Turtles have been spotted in the mangrove channels during surveys. Insect diversity includes 70 species of butterflies (Fox, 1973).(I) Globally threatened mammals (IUCN, 2002): ENDANGERED: Orang-Utan Pongo pygmaeus; VULNERABLE: Ridley's Roundleaf Bat Hipposideros ridleyi, Clouded Leopard Neofelis nebulosa, Ranee Mouse Haeromys margarettae; NEAR THREATENED: Dayak Fruit Bat Dyacopterus spadiceus, Small Woolly Bat Kerivoula intermedia, Bronzed Tube-nosed Bat Murina aenea, Large Brown Myotis Myotis montivagus, Ridley's Myotis Myotis ridleyi, Ridley's Roundleaf Bat Hipposideros ridleyi, [Hairy-winged Bat Harpiocephalus mordax]; DATA DEFICIENT: Malayan Sun Bear Helarctos malayanus (II) Globally threatened reptiles (IUCN, 2002): No information.(III) Globally threatened plants (IUCN, 2002): ENDANGERED: Dryobalanops lanceolata; VULNERABLE: Eusideroxylon zwageriNote: [ ] = unconfirmed record.
BirdLife International (2019) Important Bird Areas factsheet: Kabili-Sepilok. Downloaded from http://www.birdlife.org on 18/08/2019.