Located on the Mangkalihat peninsula on the border between Kabupaten Kutai and Kabupaten Berau. Karst mountains in this area are very spectacular, lowland limestone plains from Semenanjung Sangkulirang is a representative of the unique habitat of Sundaic region. Conservation action for this area is really needed. Caves with evidence of prehistoric human activities can be faond in this area. MacKinnon (1997) considere that this area need to considered as globally conservation priority.
It probably support sub-alpine birds species rather than lowland species. Great Argus Argusianus argus is a common species, as well as Moustached Hawk-cuckoo Cuculus vagans, Hodgson's Hawk-cuckoo Cuculus fugax, Gould's Bronze-cuckoo Chrysococcyx russatus. As for highland species, there are Gold-whiskered Barbet Megalaima chrysopogon (if there is no Red-crowned Barbet Megalaima rafflesii) and White-necked Babbler Stachyris leucotis - all species are slope specialist bird in Kalimantan (different in Sumatra).