Lutung budeng (Trachypithecus auratus), primata endemik Indonesia berstatus rentan (VU), menghadapi penurunan populasi sehingga studi perilaku di fasilitas konservasi ex-situ krusial untuk mendukung pelestariannya. Penelitian ini bertujuan menganalisis pola perilaku harian dan interaksi sosial tiga individu lutung budeng (jantan dewasa J1, betina dewasa B dengan neonatal, jantan muda J2) dalam kelompok dengan struktur unik di Pusat Primata Schmutzer (PPS), Taman Margasatwa Ragunan, selama Januari-Maret 2025. Pengamatan perilaku makan, istirahat, bergerak, serta interaksi sosial (afiliatif, agonistik, seksual) dilakukan menggunakan metode scan sampling dan ad-libitum, dengan analisis deskriptif kuantitatif. Hasil menunjukkan istirahat sebagai perilaku harian dominan (B 49,96%; J1 47,41%; J2 41,94%). Jantan muda (J2) menunjukkan aktivitas makan (21,38%) dan lokomosi (36,69%) tertinggi, sedangkan betina (B) menunjukkan lokomosi terendah terkait pengasuhan neonatal. Interaksi sosial didominasi perilaku afiliatif (90,63−99,77%), terutama duduk berdekatan, dengan kejadian tertinggi pada interaksi J1-B, dan tingkat agonistik yang sangat rendah. Perilaku seksual produktif hanya teramati pada interaksi J1-B, yang berkontribusi pada keberhasilan reproduksi berkelanjutan (kelahiran J2 dan neonatal). Disimpulkan bahwa lutung budeng di PPS menunjukkan adaptasi yang baik, tercermin dari perilaku alami normal, ketiadaan perilaku stereotipe, dan dinamika sosial yang stabil.

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The ebony langur (rachypithecus auratus), an endemic Indonesian primate classified as vulnerable (VU), is facing a population decline, rendering behavioural studies in ex-situ conservation facilities crucial for supporting its preservation. This research aimed to analyse the daily behavioural patterns and social interactions of three ebony langur individuals (adult male J1, adult female B with a neonate, and juvenile male J2) within a uniquely structured group at the Schmutzer Primate Centre (SPC), Taman Margasatwa Ragunan, from January to March 2025. Observations of feeding, resting, and movement behaviours, alongside social interactions (affiliative, agonistic, sexual), were conducted using scan sampling and ad-libitum methods, with quantitative descriptive analysis. The results indicated that resting was the predominant daily behaviour (B 49,96%; J1 47,41%; J2 41.94%). The juvenile male (J2) exhibited the highest levels of feeding (21,38%) and locomotion (36,69%), whilst the female (B) displayed the lowest locomotion, associated with neonatal care. Social interactions were dominated by affiliative behaviours (90,63-99,77%), primarily sitting in close proximity, with the highest frequency observed in the J1-B interaction, and very low levels of agonistic behaviour. Productive sexual behaviour was only observed in the J1-B interaction, contributing to sustained reproductive success (the births of J2 and the neonate). It was concluded that the ebony langurs at SPC demonstrate good adaptation, reflected in their normal natural behaviours, the absence of stereotypical behaviours, and stable social dynamics.