What Death Means to Primates ~ ...National Geographic ran a stunning photograph of a chimpanzee funeral. Sixteen chimpanzees – arrayed behind a wire fence – look on as workers at Cameroon’s Sanaga-Yong Chimpanzee Rescue Center show them the face of one of their dead companions. Her name was Dorothy, and the other chimpanzees had come to form “a gallery of grief” as she was wheeled by. According to Monica Szczupider, a volunteer at the center who took the photo, “[Dorothy’s] presence, and loss, was palpable, and resonated throughout the group.” The image’s meaning seemed clear; surely the chimpanzees had come to say goodbye to a friend. BoingBoing’s Xeni Jardin asked “Do chimps grieve?” and answered “Look at this photograph and just try to tell me the answer is no.” The Telegraph offered “Chimpanzees’ grief caught on camera in Cameroon,” Michael Hanlon at the Daily Mail wrote that the group was “apparently paying a sad and heart-rending tribute to their much-loved lost sister”, and ABC News promised “If you ever doubted that animals feel sorrow, this photograph will make you believe.” Dorothy’s backstory heightened the drama. Like the other chimpanzees at the rescue center, she had suffered at the hands of humans from an early age. She had spent nearly twenty five years of her life at an amusement park in Cameroon where, according to a National Geographic blog post, “she was tethered to the ground by a chain around her neck, taunted, teased, and taught to drink beer and smoke cigarettes for sport.” It was not until 2000 that she was taken in by the Sanaga-Yong Chimpanzee Rescue Center. Once she arrived, she cared for other orphans chimpanzees and was purportedly well-liked by many of the others. Chimpanzees are undoubtedly highly-intelligent, social creatures that have emotions, but what the apes in the photograph were thinking and feeling will always be a mystery to us. Remove any individual ape from the context of the photo and you would be hard-pressed to say what was going on in their minds. The context of the photo made it easy to believe that they were in mourning. To say that the chimpanzees were grieving, or were somber witnesses to a chimpanzee funeral, says more about what we wish to see than what is clearly visible. (The reaction to the photo reminded me of something that happened to a friend of mine last summer. She had gone to a reading at a New York City bookstore, but the author wasn’t very interesting and so my friend decided to leave early. As she sat up to look for a way out, though, a New York Times photographer snapped her picture. The photo ran in the paper the next day, and whoever captioned the picture wrote that my friend was sitting in rapt attention during the reading.) Relatively little is known about how social animals react to the decline and death of other individuals in their group. Chances to observe such behavior are relatively rare, and, due to the nature of the phenomenon, finding ways to do more than simply record events and associations is difficult. Still, there have been a handful of recent papers that bear on the subject of how primates – and apes in particular – respond to sickness and death. Last year James Anderson, Alasdair Gillies, and Louise Lock briefly reported on the death of an elderly female chimpanzee named Pansy. She was kept in captivity with three other chimpanzees. In November 2008, Pansy’s health began to fail and she became increasingly lethargic. There was seemingly nothing that could be done to reverse her condition, and by the evening of December 7th Pansy was close to death. Rather than isolate her, however, the head keeper chose to let the other chimpanzees – including Pansy’s daughter, Rosie – have access to the ailing female. Video cameras recorded what happened. Although each of the chimpanzees groomed Pansy close to her estimated time of death, none groomed her after she passed away. Rosie stayed near her mother’s body during the night, and the male – Chippy – aggressively displayed three times, ending each bout with an attack on Pansy’s corpse. The chimpanzees were described as acting “subdued” over the following two days, and reluctant to go into the sleeping area where Pansy died. This contrasted from recorded instances of traumatic death of wild chimpanzees – a male falling from a tree in one instance, and fatal leopard attack on a young female in another – which triggered alarm calls, aggressive displays, and left the groups highly agitated. As with the National Geographic photo, however, drawing lessons from Pansy’s death was a matter of interpretation. Anderson, Gillies, and Lock characterized the generally quiet behavior of the other chimpanzees as respect for their sick companion, and suggested that the other chimpanzees manipulated the mouth and arms of Pansy to test for signs of life. They even went so far as to suggest that Chippy’s attacks on the corpse were either attempts at resuscitation or expressions of denial and anger. The chimpanzees showed some behaviors consistent with our own reactions to death – disturbed sleep, subdued behavior and loss of appetite – but the analysis imputed emotional reactions to the animals that could not be verified. This is not to say that these chimpanzees did not experience grief or did not mourn Pansy’s death, but rather that we cannot know for sure since the thoughts and motives of the apes are unknown to us. How primates react to dead infants has been more frequently observed, and therefore slightly better-studied. In a short communication directly following the tale of Pansy’s death in Current Biology, Dora Biro and colleagues reported that chimpanzee mothers in Bossou, Guinea were observed carrying the bodies of deceased infants for so long that the remains of the little apes became mummified. This has been seen at the study site once before – in 1992 – but in 2003 two mothers both lost infants to respiratory illness and carried them for 19 and 68 days after death, respectively. By the time the mothers left the corpses, their babies were nothing more than skin and bones. Why the Bossou chimpanzees carried their dead infants for so long is unknown. They cared for the dead infants as if they were alive, yet the mothers often carried the bodies about by grabbing their limbs. This is an unusual way of carrying infants not used by mothers with living babies, leading Biro and co-authors to wonder if the chimpanzees understood that their infants were dead even as they toted them around. Chimpanzees are not the only primates that have been observed to carry dead infants for long periods of time. In 2004 Ymke Warren and Elizabeth Williamson reported similar behavior among female mountain gorillas in at Rwanda’s Karisoke Research Centre. A total of four female gorillas were seen to carry two dead infants over the course of 15 and 24 days, respectively, and both infants appear to have died during a struggle. In fact, one of the dead infants was first spotted in the arms of a female that was not its mother. The body was only retrieved by the mother six days later, and six days after that the same corpse was seen in the possession of another female. Like the mother chimpanzees, the female gorillas continued to groom the infants after death, even as they became unrecognizable. Mother geladas, too, carry mummified infants. These primates are not apes, but are a peculiar variety of primate closely related to baboons that subsists primarily on grass. They last shared a common ancestor with apes around twenty eight million years ago, yet at least some mothers have been observed to react to dead babies in the same way that the Bossou chimpanzees and Rwanda gorillas have. Just a few months ago, Peter Fashing and nine co-authors presented details from their study site at Guassa, Ethiopia where, over the course of more than three years, fourteen female geladas were seen to carry dead infants from one hour to more than 48 days. As in the apes, female geladas did not carry dead infants for a set period of time. How long they carried the bodies varied from instance to instance; many infants were quickly forgotten, but three were carried to the point of mummification. And, as with the Bossou chimpanzees, the mothers may have recognized the decaying bodies as inanimate objects. The mother geladas often carried the bodies in one hand or in the mouth, which Fashing and colleagues said are techniques never used with living infants. Furthermore, the carcass-carrying behavior was not tightly linked to the hormonal state of the mother. Biro and colleagues had suggested that the chimpanzees may have abandoned the infant bodies when they began reproductively cycling again, but this idea did not hold for the geladas. The female who carried her infant for the longest time began copulating again two weeks before abandoning the body, even carrying the smelly carcass during mating. Strangely, all the primate populations in which females have been observed to carry dead infants for extended periods live in relatively extreme environments. Mountain gorillas, geladas, and Japanese macaques – in which the behavior has also been recorded – all live in cold habitats, and all the Bossou chimpanzees carried their dead infants during the dry season. Not only did these conditions contribute to the preservation of the carcasses, but Fisher and co-authors hypothesized that there may be some kind of environmental relationship to the behavior. Because of this possibility, they warn that “researchers should be cautious about inferring a greater sense of loss or attachment in species or populations where females sometimes carry dead infants for extended periods.” What may look like an extended period of maternal grief may be a peculiarity owing to some quirk of the local habitat. The way geladas reacted to dying individuals of their own groups also raised different reasons for caution. Comparing their own observations to the summary of how Pansy the chimpanzee passed away, Fashing and co-authors explained that a mother gelada named Tesla died with almost no interest or “compassionate” care from group members. Two groupmates helped carry Tesla’s offspring as the mother gelada’s health declined due to the rupture of a parasitic swelling, but none of their groupmates seemed to notice when Tesla and her baby did not return to the sleeping cliff one day. No search for Tesla was undertaken, and her offspring only survived for one day before dying next to her mother, about 570 feet away from where their group rested. Geladas are not chimpanzees, of course, but Fashing and colleagues used Tesla’s isolated death to point out that wild primates often move over long distances to forage. They do not live in confined spaces conducive to what was inferred to be a long vigil by the side of dying individual in Pansy’s case. Life in captivity may have influenced the behavior of the purportedly grief-stricken chimpanzees, especially since no equivalent of such behavior has yet been seen in the wild. Observations of captive animals can inform our understanding of how primates respond to death, but more observations of wild primates will be essential to understanding how they react to the cessation of life. Our relationship to other primates – both living and fossil – has always been influenced by perceptions of our own species. Our primate relatives have often acted as the natural baseline by which we gauge our own behavior. Apes and monkeys either represent parts of a primitive state that our species has progressed far beyond, or they symbolize desirable aspects of an edenic, ancestral condition that we wish to return to. (One need only follow the changing presentations of bonobos and chimpanzees to see this is true – bonobos have been cast as the better angels of our primate nature, while chimpanzees have gradually become transformed into violent brutes.) We share deep connections with our primate kin – after all, we are only modified apes ourselves – but comprehending the character of our family resemblances can be fraught with difficulty. What death and grief mean to monkeys and apes is, for now, a mystery to us. @ wired/wiredscience/2011/04/what-death-means-to-primates/ By Brian Switek
Posted on: Tue, 24 Sep 2013 12:03:25 +0000
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