We use cookies on this website. If that is ok with you, just carry on.


Orangutan Reintroduction

The ultimate goal of FZS Sumatra is for every rescued orangutan to have the opportunity to return to their natural rainforest home.

Peter orang-utan release BTP
Dr. Peter Pratje with a newly released orangutan

Reintroduction to the Wild


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 field station staff quickly remove Chitos from the cage. After a medical check, he is put into the transport box. Six staff stand prepared for the arduous journey to the rainforest. Chitos and his box weigh over 80 kgs; the hike of at least two hours 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 Manggatal 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 orangutan returned to its natural habitat. From a safe distance our field assistants observe and record Chitos´ behavior. This surveillance will continue for many weeks until we can decide whether Chitos has learned enough to survive in the forest without our help.


Data collection protocol
Daily activity protocolls have been collected since the first release in 2003

The Story Continues with Post-Release-Monitoring like Behavioural Observation.....


The Frankfurt Zoological Society´s Reintroduction Project is research in action. Applied conservation is our credo; our ideas are put into practice. Purely academic questions are not our main concern. We are searching for ideas which improve our care and training methods for the orangutans so that they have the best possible chance of survival when released into the forest.


How do the orangutan do after release? Do they learn where to search for ripe fruits and how they can be opened?


To answer these questions (among others), we have trained a team of Indonesian field assistants who observe and record the orangutans´ behavior for up to 12 hours a day. The data shows us which animals are capable of an independent life in the forest and which animals still need our assistance.

Telemetry team
FZS field assistants searching for radio signals from released orangutans

.....and Radio Tracking


Once orangutans are released, we don't forget about them after the initial monitoring period. For up to two years, orangutans are tracked via a small transmitter and manual sightings are also recorded. The transmitter sends out a unique signature that can be picked up by radio telemetry equipment. The position of the orangutan is established by taking several GPS readings at different positions. Back at the field station, they triangulate the location of the orangutan to get the most accurate reading. The information is recorded in a database and the consolidated data is used by our GIS staff to build maps of orangutan distribution and dispersion.


This way, we can help them make a smooth and safe transition from the jungle school sessions to full-time, independent jungle living. We can track where they are, how they are moving around and exploring territory, visit with worming tablets and check on their condition. In their first year they also sometimes need supplementary feeding and a few vitamins to get them through time when fruit is scarce.