Sita and Momon nibble contentedly on the freshly peeled rotan-stem without pricking their lips on the sharp thorns, almost in the same way a wild Sumatran orang-utan would do. They have received the rotan from Damson, an Indonesian field assistant working for the Frankfurt Zoological Society. Damson is preparing the orang-utans for an independent life in the wild. After the rotan lesson, Damson brings the pair freshly opened termite nests. Momon and Sita are very interested and pounce on the new food source with enthusiasm. Damson hardly needs to show them how to suck the termites out of their tunnels; after three months of training, this task has become routine.

Rotan is a very important food source for the orang-utans in Bukit Tigapuluh. In contrast to most fruits, which are only seasonally available, rotan grows all year-round in large clumps along river banks. Unfortunately, most hand-reared orang-utans have no idea what rotan is. When fruits become scarce, rotan becomes a valuable source of nourishment.

Termites are another important foodstuff that our oran-utans have to get to know before they are reintroduced into the forest – it is an alternative food source in the months where no ripe fruit is to be found. Orang-utans have difficulty adjusting to new foods. We show the animals what to do until they have learnt, by immitation, to enjoy the new delicacies.