Chitos suddenly turns around, pulls the long needle out of his thigh and angrily chews on it. After five minutes his movements become slower and more uncoordinated and he sinks to the cage floor. We have anaesthetised Chitos with the help of a blowpipe and –syringe. Today is a big day – he is returning to the forest.

Two station helpers quickly remove Chitos from the cage. After a quick medical check, he is put into the transport box. Six helpers stand prepared for the arduous journey to the rainforest. Chitos and his box weigh over 80 kgs; the 40 minute hike in tropical humidity is no easy task.

To make Chitos comfortable in his new surroundings, we have built a bamboo platform on the bank of the Pengian River and covered this with fruit. We place Chitos´ box on the leaf-littered forest floor, open the aluminium door a small slit and hide ourselves. After a while, Chitos opens the door and makes his way to the platform by climbing a tree. We´ve done it! Another orang-utan returned to its natural habitat. From a safe distance our scientific assistants, Isa and Yossia, observe and record Chitos´ behavior. This surveillance will continue for many weeks until we can decide whether Chitos is smart enough to survive in the forest without our help.