Siamang (Symphalangus syndactylus Raffles, 1821) merupakan spesies endemik asal Sumatera yang berstatus terancam/endangered akibat adanya degradasi habitat, fragmentasi, urbanisasi, hingga perburuan dan perdagangan hewan. Telah dilakukan penelitian mengenai interaksi siamang jantan dan betina serta pengaruh duet vokalisasi siamang di Zona Primata Gembira Loka Zoo Yogyakarta. Penelitian bertujuan untuk menganalisis perilaku interaksi jantan-betina pada siamang, menganalisis adanya kaitan interaksi jantan-betina siamang terhadap vokalisasinya, dan mengidentifikasi serta menganalisis keberadaan pengaruh yang diakibatkan duet vokalisasi siamang terhadap vokalisasi hewan lain dalam Zona Primata Gembira Loka Zoo Yogyakarta. Penelitian dilakukan terhadap sepasang individu siamang jantan dan betina menggunakan kombinasi metode scan sampling, ad-libitum sampling, dan all occurrence sampling dengan 30 pengulangan pada periode Januari sampai Maret 2024, pukul 09.00 – 15.00 WIB. Hasil penelitian menunjukkan bahwa jenis perilaku interaktif dengan total frekuensi tertinggi adalah approaching (436) dan terendah sharing food (0). Duet teramati pada 20 kali pengulangan dan selalu terjadi secara bersahutan dengan owa kalimantan (Hylobates albibarbis) yang letak kandangnya berdekatan. Adapun perilaku mating, berupa mounting hingga kopulasi, teramati pada sebagian besar pengulangan, dengan kopulasi yang berhasil teramati sebanyak sepuluh kali. Berdasarkan hasil tersebut, diketahui bahwa sebagian besar interaksi siamang jantan dan betina dilakukan dalam kondisi close proximity, termasuk dalam melakukan duet. Duet yang dilakukan siamang dapat terdengar oleh H. albibarbis dan memicu vokalisasi balasan dari H. albibarbis sehingga terjadi vokalisasi secara antiphonal.

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Siamang (Symphalangus syndactylus Raffles, 1821) is an endemic species from Sumatera which has been classified as endangered species due to habitat degradation, fragmentation, urbanization, hunting, and animal trade. Research on the interaction of male and female siamang and the influence of its duet vocalizations has been conducted in the Primate Zone of Gembira Loka Zoo Yogyakarta. This research aims to analyze the behavior of male-female interactions in siamang, analyze the relationship between its male-female interactions and its vocalizations, and to identify and analyze the countercall responses on siamang’s vocalizations from other animals in the Primate Zone. The research was conducted on one pair of male and female siamang using a combination of scan sampling, ad-libitum sampling, and all occurrence sampling methods and was held on 30 repetitions for the period of January to March 2024 at 09.00—15.00 WIB. The research results show that the highest and lowest total frequency of interactive behavior is approaching (436) and sharing food (0), respectively. The duets were observed in 20 repetitions and were always been responded by their neighboring group of singing primates, the bornean gibbon (Hylobates albibarbis). Mating behaviors (mounting and copulation) were observed in most of the repetitions, with ten successful copulations observed. Based on these results, it is concluded that most of the male-female siamang interactions are carried out in close proximity, including duets. The duet performed by the siamangs were heard by H. albibarbis and triggers H. albibarbis to produce their countercalls, resulting in antiphonal vocalizations.