ESTIMASI KEPADATAN ORANGUTAN SUMATERA (Pongo abelii) BERDASARKAN SARANG DI DESA AEK SABAON KAWASAN CAGAR ALAM DOLOK SIBUAL-BUALI

Orangutan is classified as endangered species. Therefore, information of population density is ,needed. This research aimed to know the Orangutan Tapanuli (Pongo tapanuliensis) population density based on nest, the value of tree IVI (Important Value Index), and the types of dominant
vegetation used as nesting tree. Tracking begins with observed the presence of nest based on purposive sampling method. And data retrieval was done by line transect method. The results showed that the orangutan population density was 0.002 individuals / km2 or 2.348 individuals /
10ha, the highest IVI was Hayun Dolok (Syzygium sp.) with 50.39%, and the trees which mostly used by orangutan as a nest was Syzygium sp. with the number of 4 nests found in the tree (66.67%).