My other children, the orphan gorillas of Virunga

Park ranger Andre Bauma has been taking care of orphaned mountain gorillas at Virunga, Africa's oldest national park, for the past seven years, and he says he loves them as if they were his own children.

One gorilla, Ndakasi, is particularly close to Bauma. She sees him as her mother, and despite being a man - and a human to boot - he has taken on that role. "We shared the same bed, I played with her, I fed her… I can say I am her mother," he says.

They met in terrible circumstances. Ndakasi was a two-month-old infant when her mother was shot at close range through the back of the head - the park describes it as an "execution". Ndakasi was still clinging to her dead mother when they found her. "She was tiny, she only weighed a couple of kilos," says Bauma. Ever since he picked her up from the forest floor, he has dedicated his life to saving hers.

"Every single individual gorilla is crucial because it's an endangered species - so we had to take care of it, we took her in," he says.

Ndakasi was born into a renowned group of mountain gorillas called the Rugendo family, four of whose members were slaughtered in the attack in 2007 that orphaned Ndakasi.

The illegal charcoal trade is thought to have been the motive behind the shootings. Former Virunga Chief Warden Honore Mashagiro was charged but never convicted.

The law says no human activity of any kind is allowed inside the park - located in the Democratic Republic of Congo - and the rangers are there to prevent it. It's a dangerous job - since 1996, more than 130 rangers have been killed. "We are constantly threatened, not only by the militias inside the park but also in general by the population," says Bauma. "There is a lot of poverty, so people try to survive. They will try to use the natural resources of the park, whether it be wood to make charcoal, fields for agriculture or illegal fishing."

Bauma now heads the gorilla orphanage, located at the park headquarters in Rumangabo. Ndakasi was the first to be housed there, but she was soon joined by Ndeze, another member of the Rugendo family. In 2010 the two females were joined by Maisha, another female, and Kaboko, a male - both had been seized by poachers, and Kaboko had lost his hand in a snare. Kaboko died in 2012, but since then another orphan has joined the gang - Matabishi, a young male found abandoned outside the park.

No-one believed Ndakasi would survive, but she has grown to be a healthy 65kg. She still behaves like a baby, though. "Whenever she sees me she climbs on my back like she would with her mother," says Bauma. "But she's a big and strong girl and I'm not capable of playing with her like I used to. When she climbs on my back, every time I'm worried that I'm going to hurt myself - in fact at the end of the day I have real backache."

The rangers communicate with the gorillas using a combination of gestures and voice commands.

"For instance there is the approaching call to tell them: 'Here I am, I'm coming, I'm going to stand next to you, there's no problem everything's fine,'" says Bauma - this sounds like a long, low grunt. "I can also forbid them something," he says. "I can tell them: 'This is not good, you mustn't do this.'" That command sounds like a series of short uhs.

In fact, communicating is not a problem at all, says Bauma. "I find them very intelligent and I can understand anything. I can hear by their tone of voice if they're scared of something, if they're worried, if there's something wrong with the food, if they feel they're in danger… There are different sounds they make and because we've lived together for so long I'm quite good at recognising their mood."

If the gorillas misbehave, manhandling them is not an option - the orphans are now stronger than their human carers. "You cannot force them to do something because if they decide to be stubborn, you will have difficulties," says Bauma. For example if an orphan escapes from the enclosure, it can take hours to get them back inside - it's the gorillas' "favourite game" according to the park website, but it's not at all funny for the carers.

Luckily Bauma has a secret weapon: Pringles - the salty potato snacks. "When you give them something they like, they realise that you're their friend. We do not give it to them as food, but rather as a tactic to handle them," he says.

Virunga National Park is one of the most biologically diverse protected areas on the planet. It was set up in 1925 primarily to protect the mountain gorilla, and about a quarter of the world's 890 remaining mountain gorillas live within it. According to WWF, one of the animals can indirectly generate £2.5m ($4m) in tourist income over its lifetime - and in the 1970s the park was popular, welcoming an average of 6,500 visitors per year. But it suffered terribly from the decades of conflict that followed.

The gorilla killings in 2007 proved a turning point. A new director of the park was appointed and its fortunes revived. Tourist numbers rose back into the thousands, but in 2012 a new rebel movement called M23 moved into Virunga and the park closed to visitors. At the same time, the park was facing the threat of oil exploration from a UK company.

These turbulent times have been documented in a new film, called Virunga, directed by Orlando von Einsiedel and with Leonardo Di Caprio as executive producer. The film premiered worldwide on Netflix on Friday.

The gorilla orphanage is at the heart of the film. As the M23 insurgency draws nearer to the park's headquarters, Bauma is seen comforting a frightened young gorilla. "We are very worried about the fighting, we are hearing so many bombs, many many many bombs," he says, stroking the gorilla's hair.

Eventually the M23 militia comes so close that everyone in the area is evacuated - except the rangers, armed with rifles. "I felt obliged to stay with the gorillas here," Bauma says. "You must justify why you are on this earth - gorillas justify why I am here, they are my life. So if it is about dying, I will die for the gorillas."

The film shows local people running into the park for help - veterinary facilities are used to treat the wounded. But in the end there was no conflict with the militia. "First of all we don't have the means to fight them, so we chose another solution," says Bauma. "We tried to explain to them that we are not politicians, we are people trying to preserve nature, and nature belongs to everyone, to all the Congolese and the people in the world. Things went fairly well, while they were there they didn't do too much damage, because we chose that peaceful approach."

In October 2013 the army recaptured Rumangabo from the M23 rebels. And according to a joint statement with the WWF, UK oil company Soco has committed to end its oil exploration operations in Virunga. But for the park to be safe in the long term, Unesco has called for the Congolese government to abandon all plans for oil extraction. And the park still has its enemies. In April the park's director Emmanuel de Merode was shot and wounded in an ambush.

Bauma says it's hard to decide what to do with the orphans in the long term. "Our goal was always to eventually release them into the wild," he says. However the rangers' efforts to make the gorillas grow strong may have backfired.

"The way we fed them, it was mostly food that we buy at the market - fruit, carrots, apples - and it's not really food they can find in the wild. Also, they sleep inside the house at night so there's a real concern. Now we've realised that if we were to release them into the wild they could have a problem with the food, and they could have a problem with the weather - they could die."

It has been decided that the orphans should stay in their sanctuary for now. This means that Bauma will carry on spending three weeks in Virunga with his gorilla family and a week at home with his human family. Are they ever jealous? "My human family understand that my work with the gorillas is important," he says. "I wouldn't say that I love the gorillas more than my human family but I do try and find a balance - they are both very important to me. I have a share of love that I give to my gorilla family and a share of love that I give to my human family."

Andre Bauma appeared on Outlook on the BBC World Service. Listen to the interview again on iPlayer or get the Outlook podcast.

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