He was five months old when he was discovered, days before Christmas, crammed into a wooden crate in the cargo section of a Turkish Airlines plane en route from Nigeria to Thailand, his terrified face making headlines across Turkey and beyond.

Nearly nine months on and Zeytin (Turkish for olive), as he was named, is an entirely different creature from the traumatised infant brought to Polonezkoy Zoo in the hills outside Istanbul to recover from his trafficking ordeal.

His recovery means he will be soon sent back to Nigeria where he began his journey, Turkish officials say.

Zeytin is believed to be a Western lowland gorilla, a critically endangered subspecies native to the rain forests of central Africa whose numbers have plummeted in recent decades because of deforestation, hunting and disease.

West and Central Africa are major sources of trafficking, with a 2013 UN environment programme report -- the latest official figures available -- saying 3,174 great apes were lost annually to illegal trade, based on the numbers seized, with a great many more going undetected.

"It was the first time a gorilla has been confiscated at Istanbul airport," Fahrettin Ulu, regional director of Istanbul's Nature Conservation and National Parks directorate, told AFP.

"He was found inside a small box and he was terrified: you could see it in his eyes."

The baby gorilla was moved into a special section within the zoo where he was "nurtured with motherly affection", he said.

"When he first arrived, he weighed 9.4 kilograms and now he weighs 16. And his height has increased from 62.5 to 80 centimetres. In other words, Zeytin, who was once a baby, has become a young gorilla."

Inside an open area of the zoo, Zeytin races across the grass like an energetic toddler, swinging from nearby tree branches and playing tag with his keeper, only occasionally slowing down to munch on a piece of cucumber or orange.

Ulu explained that under the CITES treaty limiting the trade of protected species, animals rescued from trafficking must be sent back to the exporting country.

The repatriation process, he said, was being coordinated with the Nigerian authorities and the CITES Secretariat.

"We followed the legal procedures and investigated information regarding the rehabilitation centre in Nigeria, after which we decided to send him back," he said.

- Gorillas targeted -

According to UK-based monitoring group TRAFFIC, buyers are increasingly looking to acquire baby great apes as pets, or for zoos, circuses, shows -- or to use for social media content.

"Gorilla babies can be trafficked easily because they are young, very manageable and easy to transport so the trend is increasing," said Denis Mahonghol, TRAFFIC's central Africa director, adding that the trade was "increasingly linked to organised crime networks".

Although the Turkish authorities have said Zeytin will be repatriated later this month, Mahonghol said the date remained unclear.

He said the Nigerian authorities had told his organisation they were still waiting for Turkey to supply the timeline.

To ensure a safe repatriation process, it was crucial for the country of seizure to work closely with the country of origin, which should have its own rescue facilities in place or support from a suitable local NGO, he said.

"In the case of this gorilla, the first thing is to put him in a quarantine area in a rescue centre, and secondly to carry out DNA testing to confirm his origin," Mahonghol told AFP.

- Companionship awaits -

An NGO called Pandrillus Foundation will temporarily care for the gorilla, carry out the testing and release him into the wild, he said.

Pandrillus Foundation director Liza Gadsby told AFP they were waiting for Zeytin's arrival and would house him with another young gorilla of the same subspecies.

"At Drill Ranch we have another gorilla, a three-year-old female named Bili who was confiscated by customs in Lagos two years ago. DNA testing has shown she is a Western lowland gorilla," she told AFP, saying it was "highly likely" that testing would confirm the same of Zeytin.

"We postponed our plans to transfer Bili to a habitat country sanctuary when we learnt of Zeytin so that he could join her while completing his quarantine. They would both benefit immensely from being together before their next transition," she explained.

"These two little orphans have suffered so much already in their very young lives."

burs-hmw-fvl/jxb

TURKISH AIRLINES - TURK HAVA YOLLARI AO