BOS Wanariset was the very first project of BOS. It was established to help the many orangutan orphans confiscated by the government and to attempt to rehabilitate and release them back into the forest. Most of the orangutans in the rehabilitation center were either confiscated by the Department of Forestry or handed over voluntarily to the project by (local) people who held them as pets, while not insignificant numbers were returned from other countries like Taiwan, Hong Kong, Thailand and others.

1. Quarantine
All the orangutans that arrive at the Center are placed in isolated quarantine cages. They are given complete physical and clinical examinations, are fingerprinted for identification and tested for infectious diseases like Hepatitis A, B, C, and tuberculosis and a variety of other problems such as bullets, parasites, etc. The period of time spent in quarantine is usually two or three weeks, dependent upon laboratory test results. Healthy orangutans can then proceed to the socialization stages. Orangutans who do not pass the medical check are kept in quarantine or transferred to the clinic for treatment. Infant orangutans are transferred to the Babies Room for one-on-one care until they are old enough to move to the socialization stages.

2. Socialization
Once they have cleared the medical check, the orangutans are placed in forest socialization cages or Forest Schools with animals of a similar age and temperament. The vast majority of orangutans arriving at the Center are under ten years of age; therefore they are still in need of some social interaction and learning. For young babies, the socialization stage gives them companionship with other youngsters as well as the care from a substitute mother. During this period they are given leaves to encourage nest building and are introduced to many wild fruits and leaves eaten by wild orangutans in the forest. The animals are observed and records are kept of individual development. Orangutans may spend between three to ten months (sometimes more) in the socialization phases dependent upon individual needs and physical development.

3. Forest Schools (Sekolah Hutan)
The Forest Schools are areas within Samboja Lestari that have been designated for use by orangutans for skill learning in a natural forest. During the daylight hours orangutans are free to move in the trees (under supervision as data is collected daily) to gain much needed forest expertise. They are taken to sleeping cages only at sundown, where a motivating evening snack is awaiting them and where they eagerly and voluntarily walk towards.

4. Halfway House
The older orangutans who have exhibited forest skills such as nest building, climbing trees, etc., are moved to the Halfway House. The Halfway house is a small forest where orangutans continue to learn more about finding foods on their own and living in a ‘real’ forest. The average time an orangutan spends in the Halfway House is 6 months (sometimes more) dependent upon the availability and suitability of release sites.

5. Release
The final release phase occurs when a suitable site is found and orangutans have shown the required elements to survive in a natural forest. Orangutans that are release candidates are grouped according to correct sex ratio and size/age. All release sites are studied initially to ensure the availability of fruit trees and fallback foods. As an important official requirement and recommendation under the IUCN (International Union for the Conservation of Nature) there should be no viable wild populations of orangutans in any release site and the site should be geographically isolated from wild populations.