Described as valley and and mountains up to more than 2500 m elevation. There are some Dayak villages in this area. Dominated by slope area from 200 m elevation up to the top of Gunung Lognawan (2558 m), that cross the country boundary to Pulong Tau reserve in Sarawak (Malaysia).
It is predicted that almost all of Kalimantan endemic species can be found in this area, which some species are recorded near the boundary (Pfeffer 1960-1961). Some of the species which have been already confirmed by van Balen (1997) are Besra Accipiter virgatus, Large Hawk-cuckoo Cuculus sparverioides, Mountain Scops-owl Otus spilocephalus, Whitehead's Trogon Harpactes whiteheadi, Golden-naped Barbet Megalaima pulcherrima, Whitehead's Broadbill Calyptomena whiteheadi, Grey-chinned Minivet Pericrocotus solaris, Blue-winged Leafbird Chloropsis cochinchinensis (sub species flavocincta, described as full species by Inskipp et.al. 1996), Eyebrowed Jungle-flycatcher Rhinomyias gularis, Whitehead's Spiderhunter Arachnothera juliae, and ucommon upper mountain species Tawny-breasted Parrot finch Erythrura hyperythra.
Non-bird biodiversity: Tupaia dorsalis, Tupaia montana, Tupaia picta, Pipistrellus kitcheneri, Nasalis larvatus, Presbytis frontata, Presbytis hosei, Presbytis rubicunda, Hylobathes muelleri, Neofelis nebulosa, Bos javanicus, Muntiacus atherodes, Maxomys ochraceiventer, Callosciurus adamsi, Callosciurus baluensis, Callosciurus orestes, Exilisciurus whiteheadi, Ophiophagus hannah, Tomistoma schlegelii (Colijn 2000).
BirdLife International (2019) Important Bird Areas factsheet: Kayan Mentarang. Downloaded from http://www.birdlife.org on 16/02/2019.