Siamang
Hylobates syndactylus

This is the largest gibbon, both male and female are black.  They live in primary and secondary lowland forests and montane forests up to 3600m.

They eat 60% leaves, 30% fruits, 8% flowers and 3% animal prey.  The Siamang, as all gibbons, only lives in pairs, one male, one female with offspring in a family group. They are tree dwellers.

Siamang inflate their throat sac to make their 'great call', they have possibly the loudest voice of all primates.  This is used to communicate possession of territory.

Males and females have differing songs.  Siamang live in Sumatra and a small pocket on the Malay peninsula.

The sounds you can hear surrounding these when visiting the zoo were recorded by the zoo director, whilst visiting the Sumatran Tiger Project in Way Kambas National Park, Sumatra.  There is a vibrant, yet vulnerable, population of Siamang there, possibly towards 300 pairs.