This work is licensed under a Creative Commons Attribution 4.0 International License [98] Jurnal Belantara Vol. 4, No. 2, Agustus 2021 (98-112) E-ISSN 2614-3453 DOI: 10.29303/jbl.v4i2.811 P-ISSN 2614-7238 Terakreditasi (SK No.148/M/KPT/2020) NESTING BEHAVIORAL ADAPTATIONS OF ORANGUTAN ( PONGO PYGMAEUS MORIO) IN COAL MINING AREA IN EAST KALIMANTAN Liza niningsih 1* , Sri Suci Utami Atmoko 2 , Hadi S. Alikodra 3 , & Yeni A. Mulyani 3 1 Department of Forestry, Kutai Timur College of Agricultural, Sangatta, Kutai Timur 75683, Kalimantan Timur, Indonesia. 2 Faculty of Biology, Nasional University, Pasar Minggu, Jakarta 12520. 3 Department of Conservation of Forest Resources and Ecosystem, Faculty of Forestry, IPB University, Campus IPB Dramaga, Bogor 16680. * Email : lizaniningsih@stiperkutim.ac.id. Received: 19/01/2021, Revised: 06/07/2021 Accepted: 07/07/2021 ABSTRACT Coal mining changed forest structure and composition, it caused large negative impacts on the orangutan. In order to mitigate those negative effects, it is crucial to understand their nesting behavior adaptation in mining area. We investigated 74 times nested event in coal mining rehabilition area (CMRA) in East Kutai and 123 times in the Kutai National Park (Prevab) from October 2013 to September 2014 and include only night nests. We compared both habitats. Orangutans in CMRA built the nest later than in Prevab and used 15 species of trees as nests sites intensively on Senna siamea and Gmelina arborea. In Prevab, 35 species with the higher frequencies on Eusideroxylon zwageri and Dracontomelon dao. The average diameter of nest trees in CMRA smaller than Prevab. The height of nest trees in CMRA with the highest frequency was in 10.1-15 m, while in Prevab was as in 20.1-25 m. Orangutans in CMRA nested at the height of <15 m, lower than in Prevab was >20 m. Reused nest in CMRA was higher than in Prevab. Orangutans in CMRA more often built nests at the peak and limb, while in Prevab at the limb and peak. Orangutans in CMRA had learned to utilize various species and dimensions of trees as the place to build nests. Keywords: habitat change, nest trees, night nest. INTRODUCTION The great apes build night nests exclusively on the trees (Tutin & Fernandez 1984; Hall et al. 1998; Poulsen & Clark 2004). Theoretically, one of their reasons establishes it is an anti-predators strategy (Anderson 2000). The natural predator of Bornean orangutan that has been reported is Neofelis diardi (MacKinnon 1974; van Schaik 1983). Other motives are to avoid contact with nocturnal frugivores (Anderson 2000), to comfort sleep (Stewart et al. 2007), to better sleep quality (Anderson 1998), and as an anti-vector of diseases (McGrew 2004). The nest structure is important to increase the security of great apes during sleeping (Baldwin et al. 1981). Orangutans built nests every day and become a reliable indicator of their existence in an area (MacKinnon 1974; Ancrenaz et al. 2004; Morrogh-Bernard et al. 2009). The