Siamangs are the largest gibbons and form lifelong monogamous pair bonds reinforced by elaborate duet calls. Zoo welfare depends on stable pair or family housing, extensive climbing structures, and acoustic management.
Siamang welfare in captivity centres on pair bond integrity, calling opportunity, and arboreal space. The monogamous pair bond is not merely social preference but a core element of siamang biology — separated bonded pairs show acute distress, reduced feeding, and disrupted sleep. Pair introductions must be managed with great care, and established bonds should not be broken without compelling welfare justification. Calling is a daily motivated behaviour that siamangs must be able to express — suppressing calls through noise management or exhibit design causes frustration. Zoos must balance this with neighbour considerations. Enclosures must enable true brachiation — rope systems, overhead bars, and elevated structures at multiple heights allow natural locomotion. Ground-level exhibits are inappropriate for this species. Breeding management within AZA and EAZA SSP programmes coordinates pairings to maintain genetic diversity in the captive population that serves as a safety net for Sumatran populations.