They pout, tilt their heads, and turn one hip to the camera for a slimmer silhouette, their brown hair catching the light as they pose for a selfie.

But these are no tourists: they are Ndakazi and Ndeze, two orphaned gorillas in Virunga national park in the Democratic Republic of the Congo. And they forgot to suck their bellies in.

The “gorilla selfie” went viral after it was shared by Mathieu Shamavu, the ranger who captured it.

Shamavu said he was checking his phone when he noticed Ndakazi and Ndeze mimicking his movements behind them, so he took a picture with them.

Virunga, Africa’s oldest national park, is home to a rare population of about 1,000 mountain gorillas, but its location in eastern DRC means they and the rangers who protect and care for them are constantly at risk. Poaching, illegal charcoal smuggling and the threat of Mai-Mai militias are some of the threats to their survival.

According to rangers at the sanctuary, Ndakazi and Ndeze were the first to be cared for at the Senkwekwe Mountain Gorilla Orphanage Centre, the only one of its kind in the world. Nkakazi and Ndeze were orphaned 12 years ago when their families were killed by poachers.

Because the gorillas have such close contact with rangers and caretakers from a young age, they learn to imitate humans.

“In terms of behaviour, they like to mimic everything that is happening, everything we do,” Shamavu said.

He said the caretakers at the orphanage try to give the animals as much access as possible to their natural environment, but they inevitably exhibit “almost the same behaviour as humans”.

They need constant care, so the rangers live nearby and spend their days feeding them, playing with them and keeping them company.

“Gorilla caretakers with those gorilla orphans, we are the same family,” said Andre Bauma, the head caretaker. “They know we are their mum. They are a member of the family. We are their friends.”

Virunga is Africa’s most biodiverse national park, spanning tropical forests, snow-peaked mountains and active volcanoes. It is also one of the last homes of wild mountain gorillas, with other wild populations elsewhere in the Congo, Rwanda and Uganda.

Virunga’s management has had to take extraordinary measures to keep its visitors safe from the sporadic fighting in the region – protecting them with a highly trained guard of elite rangers and sniffer dogs, as well as working closely with communities surrounding the park.

Last May a park ranger was killed by gunmen, and two British tourists and a Congolese driver were briefly held captive. The park closed until it could secure the safety of visitors, and reopened in mid-February.

The park, which relies on private visitor donations, used its “gorilla selfie” moment in the spotlight to help raise funds, reaching its $50,000 (£39,000) target to mark Earth Day.