In a tender and unusual moment, a formidable silverback gently grooms his infant son whose mother has died.

Filmmakers captured the rarely-witnessed scene while recording a family of endangered Grauer’s gorillas (Gorilla beringei graueri) in Kahuzi-Biega National Park in the Democratic Republic of Congo for a new BBC series 'Gorilla Family & Me'.

A close relationship developed between 30-year-old dominant male gorilla Chimanuka and his infant son Marhale after the youngster’s mother died when he was just aged 17 months old.

Marhale's mother is thought to have been killed during a fight between Chimanuka and a rival silverback.

Without his mother’s milk, he was left malnourished and struggling to thrive. Although the little gorilla is part of a large family of about 25 individuals, female gorillas have never been seen to adopt an infant that isn’t their own. So the silverback Chimanuka has taken the unusual step of caring for his son, aged three at the time of filming, by shouldering the extra parental duties of a mother gorilla.

These include grooming and allowing his son to follow him closely. By watching Chimanuka, Marhale has learned how to feed himself with forest vegetation.

In gorilla society, a dominant male’s role is mainly to use their size and brute strength to protect the family unit. Male Grauer’s gorillas, the largest primates in the world, can weigh over 225kg (roughly 500lb), and are about three times heavier and eight times stronger than a human.

But without Chimanuka’s tender and patient touch it is unlikely Marhale would have survived.

Now it is hoped the youngster will have several more years by his father’s side until the time comes for him to leave his family, a step all adolescent male gorillas must take.

Although similar bonds between male gorillas and their offspring have been recorded in other, better-studied subspecies, this is the only known occurrence in the threatened and rarely-seen Grauer’s gorilla, found only in the rainforests of eastern DR Congo.

‘Gorilla Family & Me’ begins in the UK on BBC Two, Monday 21 December at 21:00 GMT.

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