Wild N. gracilis and N. mirabilis

[allenphoon]

Tan, i ,might know why there got a lot of sounds during our travel, it must be Siamang!!!
copy and paste from wikipedia.com
Role of calling

The Siamang starts its day by calling in the early morning and calls less after midday, with the peak of their calls around 9:00 am to 10:00 am. Most of the Siamang's calls are directed to its neighbours rather than to inside its home range. This means that the Siamang's calling is in response to disturbances and is to defend its territory. Calls in the late morning typically happen when it meets or sees another Siamang group. The edge of the Siamang's home range, which may overlap another, is often the places where calling is made. Counter-call (co-response calling) occasionally happens near the border or in the overlap area. Calls are numerous when fruit is more abundant rather than when fruit is less available. Branch shaking, swinging, and moving around the tree crowns accompany the calling. This movement might be to show the other groups where they are.
The Siamang prefers calling in the living, high and big trees, it might be the places where another group is easy to see. Beside that, living, big, and tall trees can support Siamang movement. Calling trees are usually near feeding trees but sometimes they call in the feeding trees