The death of a mother chimpanzee usually proves fatal for her babies.
Rarely do other female chimps step in to adopt orphans, and adult males are too busy trying to establish their supremacy within the group.
So when "Oscar", the tiny star of a major new film about chimpanzees, was orphaned two years into a three-year shoot in an African rainforest, dismayed film-makers feared that he faced certain death. Then in stepped "Freddy", the group's dominant male, with a display of tenderness never before captured on camera, astonishing the leading scientists and the largely British film crew making a Disney film to be released in the UK on 3 May.
Chimpanzee is delighting scientists because such an adoption is so rare. To become the alpha male within his group of 37 chimpanzees, Freddy had displayed great aggression towards other males in the group, while appearing not to notice the presence of Oscar. But when the baby was left terrified and vulnerable after his mother was killed – possibly by a leopard – the film-makers and scientists watched in amazement as Freddy began to show an altruistic, gentle side he had never before displayed. He allowed tiny Oscar to ride on his back, bending his knee to help him climb up, cracked nuts for him, delicately groomed him and shared his nest at night, his massive, muscular arms cradling the sleeping baby.
Filming took place primarily in the Taï Forest, a Unesco World Heritage Site in Africa's Ivory Coast, where Professor Christophe Boesch, a renowned chimpanzee expert and the film's principal scientific consultant, has studied chimps for 33 years. He said: "I have never seen a male like Freddy take up the role of a mother like that."
Oscar was just two and a half when orphaned. Chimpanzees are so dependent on their mothers that they generally cannot survive if they are orphaned before the age of five. Sometimes other females or older siblings will adopt them, but genetic tests proved that Oscar and Freddy are not related. The adoption was captured on film by Martyn Colbeck, a British cinematographer whose wildlife productions over 25 years include Planet Earth and Frozen Planet.
Filming was gruelling physically. Over 700 days across three years, the crew faced swarms of aggressive bees, torrential rain, extreme humidity, and deadly snakes as they struggled to keep up with chimpanzees who travel up to 15 miles a day. Colbeck said: "The relationship between these two animals actually made that pain worth it." To avoid spreading disease, the film-makers always kept their distance and wore surgical facemasks.
In the film, directed by Alastair Fothergill and Mark Linfield, science meets entertainment. It is the fourth production from Disney's Disneynature division, launched in 2008, and continues the tradition of the company's founder, Walt Disney, who was a pioneer of wildlife documentary film-making.
Chimpanzee, which follows the box-office success of Earth, Oceans and African Cats, has already made $30m (£20m) in America alone. Disney is donating hundreds of thousands of dollars from those proceeds to the Jane Goodall Institute's "See Chimpanzee, Save Chimpanzees" cause.
The studio hopes that the film will raise awareness of the chimpanzees' plight. Over 50 years their number, once a million in the wild, has reduced to 200,000. In two more decades, they will become extinct in 10 countries, through hunting, disease and encroachment on their habitat. Boesch said: "The more people see the film, the more people will fall in love with chimps, maybe wanting to help them." Taï Forest chimps have some fascinating habits such as helping injured fellows by putting saliva on wounds, and carrying stone tools for miles for cracking nuts.
Whether Oscar inherits his adoptive father's altruism remains to be seen. He will become an adult only at 15 and is still a feisty, funny juvenile. As for Freddy, having discovered his caring side, he has been demoted within the group and is no longer alpha male.
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