On the 7^th of December, 2008, in the heart of Scotland, a chimpanzee called Pansy died peacefully. She was over 50 years old and lived on an island in Blair Drummond Safari Park with three other chimps – her daughter Rosie, another adult female called Blossom, and Blossom’s son Chippie.

Their reaction to her passing was recorded by the park’s cameras (see video above) and many of their actions seem remarkably human. The others seemed to care for Pansy in her final minutes, examine her body for signs of life, and avoid the place where she died. Rosie even conducted the equivalent of an all-night vigil.

This footage provides a rare glimpse into how one of our closest relatives deal with death, and it’s one of two such examples that have been published today. The second took place several thousand miles away in the forests of Bossou, Guinea. In 2003, a respiratory epidemic killed five of the local chimps, including two babies called Jimato and Veve.

Their mothers, Jire and Vuavua, carried their babies’ lifeless bodies around for 68 and 19 days respectively. They groomed the dead youngsters and chased away the flies that circled them (see image and video below). Even after both babies had completely mummified into dry, leathery husk, the mothers still carried them, and other groups members investigated them.

These examples of quiet, calm behaviour are incredibly different from previous anecdotes. At Gombe National Park in Tanzania, the death of a male who fell from a tree was greeted by an eruption of noise. The others made alarm calls and aggressive displays, and they touched and held each other. They stared and sniffed at the corpse, but no one touched it and after four hours, the group left.

Elsewhere, in the Tai Forest, a leopard fatally mauled a young female and the same mass excitement ensued. This time, the others frequently touched the body and some males even dragged it for short distances before abandoning it. And in other cases, chimps have been shown to attack or even cannibalise the corpses of dead infants, despite the protestations of their mothers.

In stark contrast, Pansy’s peers were calm and restrained. When studying animal behaviour, it is always important to avoid the trap of anthropomorphism, but one cannot help but draw comparisons between Rosie, Blossom and Chippie’s actions and the responses of humans to peaceful death.

Pansy’s final hours were documented by Alasdair Gillies, head keeper at Blair Drummond. She started becoming lethargic in November and started receiving veterinary care. Her fellow chimps seemed to know that something was up. Instead, of sleeping on their usual platforms, they nested near her. At 4pm on December 7th, she started breathing erratically and laboriously and Gillies let the others join her.

They groomed her with unusual frequency in the 10 minutes before her death and afterwards, they seemed to test for life by inspecting her mouth and lifting her limbs. More unusually, Chippie attacked Pansy’s corpse on no less than three occasions (see video below); Gillies thinks that he may have been trying to rouse her or expressing frustration or anger. Blossom groomed her son for an extraordinary amount of time, perhaps an act of consolation or social support.

Rosie, meanwhile, stayed with her mother’s body throughout the night, on a platform that she had never previously slept on. All the three surviving chimps slept restlessly and the next morning, they were all subdued. They removed straw from Pansy’s body, ate less than normal, and watched silently as the keepers took Pansy away. When they were allowed to return to the sleeping area, Blossom and Rosie did so hesistantly, but Chippy refused. His alarm calls drew the other two back to the day area, where the trio spent the night. For the following week, none of the chimps nested on the platform where Pansy died, even though all of them had frequently done so before.

Legendary primate researcher Frans de Waal says, “I have seen chimpanzees die in captive colonies, sometimes unexpectedly and sometimes after a long illness, and the reactions described here correspond with my experiences. There is even a dramatic photograph that reached cyberspace.”

The tale of the African chimps, told by Dora Biro from the University of Oxford, differs in its details but has many parallels. Vuavua paid such care to her dead baby that by the time she abandoned him, his body was largely intact albeit mummified. Jire did the same, although she carried Jimato along for so long that his facial features were largely unrecognisable. Did Jire and Vuavua know that their babies were dead? It’s hard to say. Certainly, they seemed to treat the corpses like live babies, at least for a few days. Towards the end, they started carrying them in positions that they never use for healthy youngsters.

Other chimps touched, poked and sniffed the bodies, and lifted their immobile limbs. Some of the other youngsters even carried them in bouts of play. Even though the bodies’ were starting to deform and smell intensely, only one of the chimps ever reacted in a way that looked like repulsion (see video below). Biro never saw a single act of aggression.

This is hardly the first time that a chimp mother has been seen carrying the mummified corpse of her baby; the first such sighting was made in 1992 and was very similar to the latest ones. De Waal says, “The carrying of dead infants by chimpanzee mothers is well known, and has also been reported for other primates, although never of such long duration. 68 days is longer than any previous report that I have seen!” He says that ape physiology drives an enormous attachment between mother and infant, that doesn’t rapidly shut down when the infant dies. For example, a chimp’s reproductive cycle grinds to a halt for four years after giving birth.

“It would also not be adaptive to abandon an infant every time it gets sick,” says de Waal. “The best option is for mothers to keep hope and keep caring. A rapid shutting down of attachment would be maladaptive: it might lead mothers of near-dead infants to abandon them prematurely.” Why did Jire and Vuavua eventually let go? As their reproductive cycle restarted and all the associated hormonal changes kicked in, the mums could have been psychologically prepped to raise another generation. The fact that Jire carried her dead child for longer than Vuavua may be because she had already had 7 previous children, while Vuavua was a first-time mother.

Both of these examples suggest that chimpanzees have a better awareness of death and dying that people have previously thought. In many ways, this shouldn’t be surprising – these animals are self-aware and empathetic towards each other. Another intellgent animal, the African elephant, also shows remarkably sophisticated behaviour on the death of their peers. De Waal says, “I don’t think this is the same as what elephants do, which visit burial sites long after the death of a companion. But I wouldn’t be surprised if elephants also showed reactions like these (minus the aggressive displays, which seem typically chimp) to the actual death of another.”

Do chimps truly understand the concept of death? Based on the stories of Pansy, Jire and Vuavua, de Waal says, “Definitely, they seem to recognize the death of another, and perhaps realize that this is a permanent change, and a permanent loss. This by itself is already very significant, and reports like these help us understand the depth of their understanding.” But he also adds that we can’t draw any conclusions about whether they understand their own mortality. “To understand one’s own mortality would require extrapolating from what happens to others to one’s own situation. We cannot rule this out, of course, but it would require another big mental jump and for the moment we have no way of knowing if species other than us have made this jump.”

In the meantime, James Anderson, who led the Scottish study, says that the work could affect the way that elderly chimps in zoos and research facilities are cared for. It might, for example, be more humane to let the old-timers die naturally, surrounded by peers and familiar surroundings, than to resort to isolated treatment or euthanasia.

Reference: Current Biology, references unavailable at time of writing

• More on chimp behaviour:
• Culture shapes the tools that chimps use to get honey
• Scientists tickle apes to reveal evolutionary origins of human laughter
• Chimps use Swiss army toolkit to rob beehives
• Altruistic chimpanzees clearly help each other out
• Male chimps trade meat for sex
• Cultured chimps pass on new traditions between groups

April 26th, 2010 by Ed Yong in Animal behaviour, Animal intelligence, Animals, Chimps and other apes, Mammals | 11 comments | RSS feed | Trackback >