How chimps
deal with death: Studies offer rare glimpses
Monday, April 26, 2010
Two studies in the April 27th issue of Current
Biology, a Cell Press publication, offer rare glimpses into
the ways that chimpanzees deal with the deaths of those closest to
them. In one case, researchers describe the final hours and moment
of death of an older female chimp living in a small group at a UK
safari park as captured on video. In the other, researchers
observed as two chimpanzee mothers in the wild carried their
infants' mummified remains for a period of weeks after they were
lost to a respiratory epidemic.
"Several phenomena have at one time or another been considered as
setting humans apart from other species: reasoning ability,
language ability, tool use, cultural variation, and self-awareness,
for example, but science has provided strong evidence that the
boundaries between us and other species are nowhere near to being
as clearly defined as many people used to think," said James
Anderson of the University of Stirling in reference to his
observations of the safari park chimps. "The awareness of death is
another such psychological phenomenon. The findings we've
described, along with other observations of how chimpanzees respond
to dead and dying companions, indicate that their awareness of
death is probably more highly developed than is often suggested. It
may be related to their sense of self-awareness, shown through
phenomena such as self-recognition and empathy towards
others."
Few have witnessed chimps' response at the moment a member of their
group dies, Anderson said. Mother chimps have been known to carry
their dead infants, he said, and some observers have seen the
commotion that follows when an adult chimp is lost to some sort of
sudden trauma.
"In contrast to the frenzied, noisy responses to traumatic adult
deaths, the chimpanzees witnessing the female's death in our case
were mostly calm," Anderson said.
In the days leading up to the chimp's death, the group was very
quiet and paid close attention to her, the researchers report.
Immediately before she died, she received much grooming and
caressing from the others, who appeared to test her for signs of
life as she died. They left her soon after, but her adult daughter
returned and remained by her mother all night. When keepers removed
the mother's body the next day, the chimpanzees remained calm and
subdued. For several days they avoided sleeping on the platform
where the female had died, even though it was normally a favored
sleeping spot, and remained subdued for some time after the
death.
"In general, we found several similarities between the chimpanzees'
behavior toward the dying female, and their behavior after her
death, and some reactions of humans when faced with the demise of
an elderly group member or relative, even though chimpanzees do not
have religious beliefs or rituals surrounding death," Anderson
said. Whatever the reasons for the chimps' actions, he added, they
suggest that chimpanzees have a highly developed awareness of
death.
In the second study, Dora Biro of the University of Oxford and her
colleagues witnessed the deaths of five members (including two
infants) of a semi-isolated chimpanzee community that researchers
have been studying for over three decades in the forests
surrounding Bossou, Guinea.
"We observed the deaths of two young infants—both from a flu-like
respiratory ailment," Biro said. "In each case, our observations
showed a remarkable response by chimpanzee mothers to the death of
their infants: they continued to carry the corpses for weeks, even
months, following death."
In that time, the corpses mummified completely, and the mothers
exhibited care of the bodies reminiscent of their treatment of live
infants: they carried them everywhere during their daily
activities, groomed them, and took them into their day and night
nests during periods of rest. Over this extended period, they also
began to "let go" of the infants gradually, Biro said. They allowed
other individuals within the group to handle them more and more
frequently and tolerated longer periods of separation from them,
including instances where other infants and juveniles were allowed
to carry off and play with the corpses.
Other group members showed some interest in the bodies, but almost
without exception, the other chimps showed no aversion toward the
corpses. Biro noted that a member of her team made very similar
observations following the death of one chimpanzee infant in Bossou
back in 1992.
"Chimpanzees are humans' closest evolutionary relatives, and they
have already been shown to resemble us in many of their cognitive
functions: they empathize with others, have a sense of fairness,
and can cooperate to achieve goals," Biro said. "How they perceive
death is a fascinating question, and little data exist so far
concerning
chimpanzees' responses to the passing of familiar or related
individuals either in captivity or in the wild. Our observations
confirm the existence of an extremely powerful bond between mothers
and their offspring which can persist, remarkably, even after the
death of the infant, and they further call for efforts to elucidate
the extent to which chimpanzees understand and are affected by the
death of a close relative or group-mate. This would both have
implications for our understanding of the evolutionary origins of
human perceptions of death and provide insights into the way
chimpanzees interpret the world around them."
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Cell Press