One of the things you have to do while in Borneo is see orangutans in the rainforest. I went on a river rafting trip that included a stop at Semenggoh Wildlife Center (national park) on the way. From my research I believe this was 1 of the 2 good options for seeing wild orangutans near Kuching.
The orangutans are free in the forest. They stop by the viewing points because of the tasty food (many were also brought here for rehabilitation so they are comfortable seeing people – though the rehabilitation is largely moved elsewhere now).
Because the orangutans are free when fruit is in season sometimes few or no orangutans show up. They generally have feeding time in the morning at 9 to 10 AM (when I went) and in the afternoon (3 to 3:30 PM).