BIODIVERSITAS ISSN: 1412-033X Volume 23, Number 1, January 2022 E-ISSN: 2085-4722 Pages: 396-402 DOI: 10.13057/biodiv/d230141 Orangutan (Pongo pygmaeus wurmbii) human-oriented behavior at the Lamandau Wildlife Reserve, Indonesia NOVITA AMALIA 1, , DYAH PERWITASARI FARAJALLAH 1,3 , SRI SUCI UTAMI ATMOKO 2 1 Department of Biology, Faculty of Mathematic and Natural Sciences, Institut Pertanian Bogor. Jl. Agathis, Dramaga, Bogor 16680, West Java, Indonesia. Tel./fax.: +62-251-8622833,  email: amalianovita550@gmail.com 2 Faculty of Biology and Primate Research Center, Universitas Nasional. Jl. Sawomanila, Jakarta Selatan 12520, Jakarta, Indonesia 3 Primate Research Center, Institut Pertanian Bogor. Jl. Loday II/5, Bogor 16151, West Java, Indonesia Manuscript received: 20 October 2021. Revision accepted: 26 December 2021. Abstract. Amalia N, Fajarallah DP, Atmoko SSU. 2021. Orangutan (Pongo pygmaeus wurmbii) human-oriented behavior at the Lamandau Wildlife Reserve, Indonesia. Biodiversitas 23: 396-402. Unlike other conservation efforts, rehabilitation and reintroduction face different challenges due to humans' role in developing orphaned orangutans. Long-term interactions between orangutans and humans in captivity will gradually encourage orangutans to shape and increase human-oriented behavior (interest in humans). The Lamandau Wildlife Reserve (Lamandau WR) applies the soft-release method for the orangutan release process. Additional feed is provided every day. The correlation between animal-human interactions as part of the conservation efforts evaluation is essential to study. This study aimed to analyze the human-oriented behavior of the orangutan population in the Lamandau WR based on the observation sites (camp, feeding site, and forest) and the age-sex class of orangutans. This study also identified the factors that affected them. The study was conducted for five months (July-November 2019). During the observation, the factor of current age was suspected to affect human-oriented behavior. Human-oriented behavior is divided into three categories based on the orangutans' response: approaching, avoidance, and no response. The highest rates of human-oriented behavior in orangutans were approaching category. The highest promoting behavior was noticed at the camp and feeding site, especially young orangutans and mothers. Interest in humans can be explained by the 'captive effect' phenomenon where captive orangutans are more likely to independently explore the novelty (unfamiliar objects/foods) than their wild counterparts. Keywords: Camp, feeding site, human-oriented, Lamandau Wildlife Reserve, orangutan, reintroduction INTRODUCTION Orangutans are lifelong learners. The most important learning comes from their social experiences, especially in the immature phase when they learn to acquire ecological and social skills (Russon et al. 2016). Developing ecological abilities and knowledge of young wild orangutans in a semi-social environment depends on their mothers, especially for infant orangutans (van Noordwijk et al. 2009). At the age of 7.6 years, wild orangutan begins to be self-dependent (van Noordwiik et al. 2018). Therefore, the role of the mother becomes essential since the orangutan is born until they become self-dependent. However, the role of mother orangutans living in captivity or the rehabilitation stage is replaced by humans (Russon 2006; Morrogh-Bernard et al. 2009). The longer duration of captivity makes the effect even worse (Russon et al. 2016; Smith 2014; Palmer 2018). Prolonged contact with humans may provide a more extended period for orphaned orangutans to be socially oriented towards humans (Russon 2006; Palmer 2018). There is a wide variation in the pattern of human- animal interactions in captivity, ranging from operant conditioning training, research procedures, and regular medical treatment. The frequency of interactions that slowly occur between orangutans and humans forms a close relationship eventually (Chelluri et al. 2012; Palmer and Malone 2016). The different experiences of each orangutan with humans cause each orangutan to have different curiosity (Damerius et al. 2017; Damerius et al. 2018). Captive orangutans that build early learning with human orientation cause orangutans' physical and social development to run abnormally (Russon 2006). These factors may increase the potential for future conflict between orangutans and humans (Russon 2006). Great ape- human conflict is any interaction involving humans and great apes. Subsequent interactions will affect social, economic, cultural, ecological/environmental aspects, and conservation, which tend to be negative (Hockings & Humble 2009). Orangutan conflict with humans is a situation where the interests of humans and orangutans clash since the actions of one species may be detrimental to other species (Smith 2009). Rehabilitation and reintroduction face different challenges from other conservation efforts as the role of humans are involved in the development of orphaned orangutans (Djufri 2015; Russon et al. 2016). The dependence of orangutans on humans is a significant problem on the success of their rehabilitation and reintroduction (Russon et al. 2016; Palmer 2018). This is associated with the increased predation of orangutans due to reduced nesting ability while in the forest and ineffective