Ndakazi and Ndeze were only months-old gorillas when their mothers were killed 12 years ago.
Since then, they have lived in the Senkweke Sanctuary, a gorilla orphanage located in Virunga National Park, in the Democratic Republic of the Congo.
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Lately, the world has come to know them for their part in a selfie that two rangers took in the national park, which was posted to its Facebook page on Sunday.
“Those gorilla gals are always acting cheeky so this was the perfect shot of their personalities,” the Facebook page said.
That the gorillas were standing on two feet wasn’t necessarily surprising — most primates can comfortably walk that way for short periods, the park noted.
Their pose, however, also suggests that they’re “learning to be human beings,” Virunga National Park deputy director Innocent Mburanumwe told BBC News.
Ndakazi and Ndeke have come to see the park rangers as their parents, and have learned to imitate them, Mburanumwe explained.
The degree to which the gorillas are imitating their overseers nevertheless surprised him.
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“It’s very curious to see how a gorilla can imitate a human and stand up,” he said.
Primatologist Frans de Waal told The Washington Post that animals often mimic human caretakers.
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Not just in the way they stand, but also the expressions on their faces.
Apes are likely to do this because they have bodies similar to humans, de Waal noted.
“Apes are naturally imitative and a parent is imitated more than others,” he said.
“Imitation is often driven by attachment.”
In posting the selfie, Virunga National Park noted that the pair of gorillas live in an enclosed sanctuary where caretakers have worked to avoid putting their health in danger.
This photo, it said, was an exceptional circumstance, and gorillas should not be approached in the wild.