The two gorillas standing upright behind a park ranger in a selfie that went viral this week are orphans who constantly imitate human behaviour, their carers say. Ndakazi and Ndeze were orphaned 12 years ago when their families were killed by poachers, according to rangers at Virunga National Park in eastern Democratic Republic of the Congo. Mathieu Shamavu, the park ranger who took the photograph, said he was checking his phone when he noticed the two gorillas mimicking his movements, so he took a picture with them. The gorillas look as if they are posing for the camera and when Mr Shamavu posted the picture on social media on Saturday it quickly clocked up thousands of likes and comments. Ndakazi and Ndeze were the first orphans to be cared for at the Senkwekwe Mountain Gorilla Orphanage Centre – the only facility in the world dedicated to the care of orphaned mountain gorillas, according to Virunga park's management. As the gorillas arrive in the sanctuary at a young age, they learn from their caretakers, said Mr Shamavu. "In terms of behaviour, they like to mimic everything that is happening, everything we do," he told Associated Press. He said the caretakers try to give the animals as much access as possible to their natural environment, but they inevitably exhibit "almost the same behaviour as humans". The Senkwekwe orphanage is named after one of the wild silverback gorillas that was killed in Virunga in 2007. The orphans need constant care, so the rangers live nearby and spend their days with them – feeding them, playing with them, keeping them company. "Gorilla caretakers with those gorilla orphans, we are the same family," said head caretaker Andre Bauma. He said without their own relatives nearby, the gorillas treat the rangers as their family. "They know we are their mum. They are a member of the family. We are their friends," he said. Virunga is billed as Africa's most biodiverse national park, spanning tropical forests, snow-peaked mountains and active volcanoes. It is also one of the last bastions of wild mountain gorilla populations, along with parks in the Rwanda and Uganda. But eastern DRC has suffered from years of armed conflict. Virunga's management has had to take extraordinary measures to keep its visitors safe from the on-and-off fighting in the region – protecting them with a highly trained guard of elite rangers and sniffer dogs, and working closely with communities surrounding the park. After a park ranger was killed by gunmen and three foreign tourists were briefly held captive, the park closed until it could secure the safety of visitors. It reopened in mid-February this year. All this costs money, and the state park says it would not be able to survive without private donations from visitors. Virunga's management hopes the viral gorilla selfie will help boost the park's profile, and encourage more people to contribute to conserving the mountain gorillas and their unique natural habitat.