Maliau Basin is one of the most pristine natural features in Malaysia. The region is rugged, remote and forested and is distinguished by its circular perimeter. The Basin is sharply delimited on all sides by cliffs or very steep slopes up to 1,500 m in height. The highest point is Gunung Lutong (1,900 m asl) on the north rim. The shape had been moulded by faults and earth movements resulting in the Tanjung Formation during the early to middle Miocene age. The Tanjung Formation consists of rocks which are mudstones intercalated with thin and thicker layers of siltstone to medium-grained sandstone (Maryati Mohamed, 1998).The area is drained by radiating tributaries of the Sungai Maliau, forming a unique and important catchment for the south-central zone of Sabah. The drainage system comprises mainly of tea-coloured rivers caused by brown, humic compounds, which leach from the heath forest vegetation. Sungai Maliau gorges out of the south-eastern corner of the basin into Sungai Kuamut which in turns feeds Sungai Kinabatangan, the longest and largest river in Sabah (Maryati Mohamed, 1998; Anton and Alexander, 1998; Waidi Sinun et al., 1998). Maliau Basin also has an exceptionally high number of waterfalls.
Maliau Basin's avifaunal diversity is reflected by its habitat type, which is unique in Malaysia. Over 280 species of birds have been recorded in Maliau Basin which include several rare and endemic species (Anon., 2001, 2002; Lim-Hasegawa, 2002; Yong et al., 1989, 1998). The area also supports a diverse hornbill population (5 species) and pheasants. Other Near Threatened species found in basin includes the Oriental Darter Anhinga melanogaster and Grey-headed Fish-eagle Ichthyophaga ichthyaetus.
Non-bird biodiversity: The scientific surveys of Maliau Basin have documented several interesting findings, some which is unique to the area. 181 commercial tree species from 11 families, dominated by Araucariaceae, Dipterocarpaceae and Casuarinaceae (Barnabas Gait et al., 1998).34 species from 14 families and 26 genera of fern and fern allies (Susup Akin, 1998).The rare Rafflesia tengku-adlini has also been discovered in the area, one of only two known localities in Sabah (Marsh, 1989).35 species of freshwater algae (Anton et al., 1998).16 genera representing 10 families of bryophytes (Susup Akin and Suleiman, 1998).23 species of aquatic and semi-aquatic bugs from 7 families (Yang et al., 1998).29 species of dung beetles (Davis, 1998).37 species of butterflies from 5 families dominated by Papilionidae, Pieridae, Nymphalidae, Lycaenidae and Hesperiidae (Maryati Mohamed et al., 1998).36 species of termites (Isoptera) (Jones et al., 1998).Presence of Weaver Ants Oecophylla smaragdina in the heath forest (Widodo and Maryati Mohamed, 1998).Three species of freshwater fishes namely Puntius sealei (Cyprinidae), Betta cf. unimaculata (Belontiidae) and Hemibagrus nemurus (Bagridae) and three species of crustaceans: Parathelphusa valida (Parathelphusidae), Thelphusula sp. nov. (Gecarcinucidae) and Macrobrachiun sabanus (Palaemonidae) (Martin-Smith et al., 1998).25 species of amphibians from 5 families (Abdul-Hamid Ahmad and Wong, 1998).Four species of small mammals dominated by Whitehead's Rat Maxomys whiteheadi (Joseph Gasis et al., 1998. The presence of large and rare mammals (Marsh, 1989; Joseph Gasis et al., 1998). The area has been earmarked as an important refuge for Sumatran Rhinoceroses (WWF, 2002a).(I) Globally threatened mammals (IUCN, 2002): CRITICAL: Sumatran Rhinoceros Dicerorhinnus sumatrensis; ENDANGERED: Asian Elephant Elephas maximus, Tembadau Bos javanicus, Proboscis Monkey Nasalis larvatus, Bay Cat Catopuma badia, Orang-Utan Pongo pygmaeus; VULNERABLE: Clouded Leopard Neofelis nebulosa, Pig-tailed Macaque Macaca nemestrina; NEAR THREATENED: Bornean Gibbon Hylobates muelleri, Long-tailed Macaque M. fascicularis; DATA DEFICIENT: Hose's Langur Presbytis hosei, Malayan Sun Bear Helarctos malayanus(II) Globally threatened reptiles (IUCN, 2002): No information.(III) Globally threatened plants (IUCN, 2002): CRITICAL: Shorea platycarpa, S. johorensis, S. acuminatissima, S. almon, S. asahii, S. flemmichii, S. foxworthyi, S. platycarpa, S. smithiana, S. superba, S. waltoni, Hopea nervosa, H. beccariana, H. sangal, Parashorea malaanonan, Dipterocarpus gracilis; ENDANGERED: Shorea andulensis, S. argentifolia, S. faguetiana, S. leprosula, S. bracteolata, S. obscura, S. pauciflora, Dryobalanops lanceolata, Dipterocarpus crinitus; VULNERABLE: Durio acutifolius, D. kutejensis, Agathis dammara; NEAR THREATENED: Nepenthes veitchii, Aglaia oligophylla; LOWER RISK/conservation dependent: Nepenthes hirsuta, Koompassia excelsa, K. malaccensis; DATA DEFICIENT: Mangifera bullata
BirdLife International (2019) Important Bird Areas factsheet: Maliau Basin Conservation Area. Downloaded from http://www.birdlife.org on 19/08/2019.