• Four out of five species of great apes are now listed as critically endangered.
• The photos were then shared on The Elite AntiPoaching Units And Combat Trackers Facebook page on Thursday.
Two gorillas have been photographed posing for a relaxed selfie with the rangers who rescued them as babies.
The image was taken at a gorilla orphanage in Virunga National Park, DR Congo, where the animals were raised after poachers killed their parents.
The photos were then shared on The Elite AntiPoaching Units And Combat Trackers Facebook page on Thursday.
The park's deputy director told BBC that they had learned to imitate their carers, who have looked after them since they were found.
The gorillas, he added, think of the rangers as their parents.
Innocent Mburanumwe, deputy director of Virunga, told the BBC that the gorillas' mothers were both killed in July 2007.
The gorillas were just two and four months old at the time.
Shortly afterwards, they were found and taken to Senkwekwe Sanctuary in Virunga, where they have lived ever since.
Because they've grown up with the rangers who rescued them, MrMburanumwe added, "they are imitating the humans" - and standing on two legs is their way of "learning to be human beings".
But it "doesn't happen normally", he said.
The two gorillas named Ndakasi and Matabishi are mountain gorillas, a critically endangered species.
It is impossible not to notice how natural they act in front of the camera. And of course, how happy and safe they feel near their protectors.
However, this isn’t the first time when Ndakasi and Matabishi and the rangers are sharing some selfies time.
Ranger Shamavu also took similar pictures nine months ago with Shamavu.