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Do Chimpanzees Understand Death?

Like tool use and self-awareness, distinct grief and mourning might be just one more thing we share with our closest living relatives
chimpanzee death dying understand old



ISTOCKPHOTO/BMXFOREVER

After the death of her mother, Rosie had a fitful night, tossing and turning and getting up frequently.

That afternoon, Rosie, 20, and her mother's long-time companion, Blossom, 50, had tended to her mother as she lay dying, frequently stroking her hands and arms. Blossom's son had arrived just around the time of death and checked the body, shaking a lifeless arm. For days after the death, the three of them were relatively quiet, had little appetite and avoided the place where Rosie's mom had died.

Such a scenario has surely played out countless times in the course of human history, but the scene above comes from a new paper describing a rare documented death of an old infirmed chimpanzee and the reactions of her close family and companions

The death and surrounding chimp activity were captured on video cameras and are described in a paper published online April 26 in the journal Current Biology.

"We were surprised when we saw the reactions," says Jim Anderson, of the Department of Psychology at the University of Stirling in the U.K., and lead author of the study. Of the few previously described adult chimpanzee deaths, reactions from the rest of the group had often been quite different. Two traumatic accidental deaths in wild colonies, one of a male who fell from a tree and the other of a female who was mauled by a leopard, had elicited what Anderson describes as "frenzied excitement [and] complete mayhem" from the surrounding chimps. 

Reactions to a more timely death, however, are little known. And this rare documentation provides new insight that "calls for a reassessment of the position that only humans have death awareness," Anderson says.

"We do know that chimpanzees are capable of showing empathetic reactions" and that they have self-awareness, which might contribute to a fuller understanding of death, he explains.

Other primates, however, have been shown to continue roosting with dead compatriots, showing little regard or concern for the rotting bodies around them.

Filming the 2008 death of Pansy, who was likely over the age of 50, was in part serendipity. The chimps lived at the Blair Drummond Safari and Adventure Park in Stirling and spent most of the winters in indoor enclosures. Video cameras had been installed for a study conducted the previous year but had not been used for months. When it appeared that Pansy was close to death, the keepers decided to allow her to stay with Rosie, Blossom and Blossom's son, Chippy, 20, (rather than risk trauma in trying to capture her for more active care) and to turn on the video cameras.

That afternoon, Pansy had moved into her daughter Rosie's nest from the previous night. As Pansy's breathing became labored and her movements diminished, Rosie and Blossom sat with her, grooming her and watching her. Chippy arrived shortly before Pansy likely died. All three periodically inspected Pansy's face and limbs, with Chippy at one point touching her neck.

 


About 10 minutes later, the enclosure's lights were turned off for the evening. Chippy, who occasionally made aggressive displays when lights were dimmed, charged Pansy's corpse and pounded it with two hands before leaving the area for the night (a display, Anderson speculates, that might have been "his final effort to elicit a sign of life from Pansy").

That night, the footage shows Rosie changing her sleeping posture about a dozen times, which indicates a disturbed rest when compared to the study from the year before in which each chimpanzee in the group shifted an average of four to five times a night. The others also seemed to have relatively restless sleep.

In the morning, Chippy charged the corpse twice more just after the daytime lights were turned on, a display that might have been spurred on by "some kind of anger about the loss of an important member of the group," similar to "feelings of anger and denial and frustration toward the deceased individual" that are common in human mourning, Anderson notes. And although physical aggression is not a common human response to a relatively timely death, "chimpanzees, in general, don't have the same inhibitory constraints in their behavior as we do," he explains.

About 10 minutes after the lights were turned on for the day, keepers arrived to remove the body from the platform. The three remaining chimpanzees were "profoundly subdued" that day and remained quieter, calmer and showed reduced appetites for weeks after the death, Anderson and his colleagues noted in their paper. The remaining chimps also avoided sleeping in the area where Pansy had died even though keepers had cleaned and disinfected it.

Researchers might not ever know how much of the chimpanzees' behaviors were stemming from emotions analogous to grieving humans. But Anderson stresses the need for more research and detailed observations of these events to better understand the nuances and variations of the species' response to different types of deaths.

Another paper appearing in the same issue of Current Biology describes two mother chimpanzees carrying their dead infants in the Bossou colony in Guinea. Although this behavior has been observed in chimps and other primates before, the researchers, led by Dora Biro, a research fellow in the Department of Zoology at the University of Oxford, documented the carrying behavior for 68 days in one of the instances—far longer than had been previously described.

Of note, Biro's group reported, is that documented deaths of infants in that particular colony (of which there were three) always resulted in "extended carrying," though it is not universal that mothers carry infant corpses for weeks—or months—after death. This difference "raises questions about the potential role of observational learning in promoting chimpanzee mothers' prolonged transport of deceased young," Biro and colleagues wrote.

These differences in handling death might also be a part of demonstrated cultural differences among chimpanzee groups, Anderson says.

At the least, however, these findings suggest different ways for handling palliative care for critically ill and elderly chimpanzees in captivity, of which there are a growing number. Like the chimpanzee mothers who carry around the corpses of their infants, perhaps other chimpanzees are demonstrating behavior that helps them come to terms with the loss of a close companion or family member, Anderson notes.

The new findings, he concludes, suggest "that the differences between humans and our great ape relatives aren't as marked as most people think."

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