Abdullah, Nur Izzati, Sabapathy Dharmalingam, and Badrul Munir Md- Zain. “A Behavioral Study on the Bornean Orangutan (Pongo Pygmaeus) in a Semi-Wild Environment at Bukit Merah Orang Utan Island, Perak”. Journal of Sustainable Natural Resources 2, no. 2 (December 30, 2021): 22–30. Accessed July 1, 2022. https://publisher.uthm.edu.my/ojs/index.php/jsunr/article/view/10206.