Animal rescuers coached the 24 macaques to develop their survival skills to help them find the right food and behave as true wild animals.

British based charity International Animal Rescue saved the monkeys after their owners tired of them as a novelties or simply found them too big and dangerous to be kept as pets.

For the macaques, it has meant a long process of rehabilitation but finally they are being returned to the jungles of Indonesia to live out their lives like their wild counterparts.

Besides being quarantined and introduced to the right types of food they will need to find when foraging for real, they have also had to be socialised, perhaps for the first time in their lives. 

It meant the 18-long-tailed macaques and six pig-tailed macaques being put into four troops, with alpha male leaders, while behavioural observations were detailed by IAR’s vets and keepers to monitor their progress and time their release.

As these scenes show, the efforts have paid off with one-time pets now ready to roam free in the Batutegi Protected Forest of Lampung on Sumatra, but not before an arduous journey to ferry them in travelling cases to the right spot.

Alan Knight OBE, chief executive of International Animal Rescue, said: “Macaques are quite commonly caught and kept as pets in Indonesia. 

"Their lives in captivity are utterly miserable and we’re always delighted to be able to rescue these intelligent and sociable primates, rekindle their natural behaviours and return them to their home in the forest. 

“It is a long and painstaking process but worth all the time and effort to give these monkeys back their freedom.”

Not only are the macaques achieving liberty, their presence in natural habitat helps to restore the ecological functions of the forest environment.

After three days in habituation cages to get used to their new sounds and smells of their surroundings, the macaques are being sent free but under the watchful eye of their carers. 

IAR Indonesia’s programme manager Robithotul Huda said: “Post-release, IAR’s team also keeps track of their movements in the wild and observes their behaviour to assess how well they have adapted to their new life. 

“Usually the macaques have been close to humans for so long that they have lost the ability to behave like wild monkeys.”

Batutegi Protected Forest was selected to be the release location because of the availability important trees for the macaques.

Hilmi Mubarok, supervisor of survey, release and monitoring for IAR Indonesia, said prior to the release operation his team had conducted a survey of habitat potential and availability of natural food at the release site.

He said: “The results showed that there are various types of plants that will provide suitable natural food for the released macaques."