Penelitian pengenalan sumber pakan dan perilaku bersarang orangutan borneo Pongo pygmaeus Linnaeus, 1760 golongan umur anak tanpa induk di Sekolah Hutan Tembak, Sintang Kalimantan Barat telah dilakukan. Penelitian bertujuan untuk mengamati pengenalan sumber pakan dan perilaku bersarang orangutan anak dalam Kandang Sosialisasi dan Sekolah Hutan Tembak. Sebanyak dua orangutan anak diamati melalui metode focal animal sampling dan ad libitum. Melalui 401 jam pengamatan, hasil penelitian yang diperoleh yaitu jenis makanan kedua orangutan anak di Kandang Sosialisasi didominasi oleh buah 76,82 , sedangkan di Sekolah Hutan Tembak didominasi oleh daun 38,32 . Perilaku bersarang kedua orangutan anak di Kandang Sosial dan Sekolah Hutan Tembak cukup baik. Kedua orangutan anak mampu membuat sarang meskipun belum sampai pada tahap penguncian sarang.

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The research of explore to food sources and nesting behaviour of orphaned juvenile bornean orangutan Pongo pygmaeus Linnaeus, 1760 at Tembak Forest School, Sintang West Kalimantan has been conducted. The study aims to observe food sources exploration and nesting behaviour of juvenile orangutan in Socialization Cages and Tembak Forest School. Two juvenile orangutans were observed through focal animal sampling and ad libitum methods. With 401 hours observation, the result showed that food sources introduction at Socialization Cages of both juvenile orangutans are dominated by fruits 76,82 while at Tembak Forest School are dominated by leaves 38,32 . The nesting behaviour both of juvenile orangutans are quite good, both of juvenile orangutans are able to make nest even though it has not reached the nest locking stage.