Researchers in Scotland say a rare video of a chimpanzee dying has offered a unique glimpse into how one of man's closest relatives deals with death and grieving.
The pictures show the final hours and moment of death of an older female chimpanzee living in a small group at a British safari park.
"Many people thought that death awareness is uniquely human, so our observations are causing us to question whether the distinction in terms of death awareness between humans and non-humans is as great as people thought," said Jim Anderson, a senior lecturer at Stirling University's psychology department.
Anderson said they have observed distinctly novel behaviour because traumatic deaths have been seen before, "but never a peaceful death like this".
In contrast to the kind of commotion that follows a sudden death, the chimpanzees at Blair Drummond Safari Park, near Stirling, were mostly calm.
The footage shows group members grooming and caressing the sick female and apparently testing her for signs of life as she died. They left her soon after her death, but her adult daughter returned and remained by her mother all night.
When keepers removed the mother's corpse the next day, the chimpanzees remained calm and subdued. For several days they avoided sleeping on the platform where the female had died, though it was normally a favoured sleeping spot. They remained subdued for some time after the death.
"I was surprised that they did all gather round at the moment of death and the subsequent, you know, manipulating the body, shaking her shoulders, shaking her head as if they were trying to rouse her," said PhD student Louise Lock, who initially placed the cameras in the enclosure to study nocturnal behaviour.
The cameras were turned on by safari park staff when they realised the female chimpanzee's condition was deteriorating.
Alasdair Gillies, head keeper at Blair Drummond, said normal practice for treating animals in captivity nearing the end of their lives could now be reviewed.
"These guys have been together all of their lives," Gillies said. "I thought it is completely the wrong thing to do for these guys to be separate. So, the decision was to just let them through, all be together."
Chimpanzees are considered an endangered species with only 150,000 thought to be still living in the wild.
The researchers said watching the footage was extremely moving and may change our understanding of how our closest evolutionary relatives deal with death.
"I think what we know now," said Jim Anderson, "is that chimpanzees probably have a greater awareness of death than many people thought."
