Siamangs are the largest of the gibbon family, known for their powerful duet calls and strong pair bonds. Their welfare in captivity depends critically on appropriate social housing and acoustic expression.
Siamang welfare revolves around their profound social attachment and need for vocal expression. Pair-bonded siamangs deprived of their partner show signs of grief analogous to human bereavement — reduced activity, loss of appetite, and abnormal behaviour. The prevention of duet calling — either through inadequate acoustic design or social isolation — removes a behaviour so central to siamang identity that its suppression constitutes a significant welfare harm. Overhead locomotion on adequate structural complexity is not enrichment but a locomotor necessity for this brachiating specialist. Zoos maintaining siamangs should be required to demonstrate appropriate social, acoustic, and locomotor environments before accreditation.