Selective “mourning” behaviour in chimpanzees
Edwin van Leeuwen and Katherine Cronin (associate researchers who formerly worked in the Comparative Cognitive Anthropology group of the Max Planck Institute for Psycholinguistics in Nijmegen) conducted their observations in May 2010 at Chimfunshi Wildlife Orphanage Trust in Zambia. Wild-born chimpanzees, who have been rescued from illegal trade, live in this orphanage in the largest social groups and enclosures in the world.
The researchers previously reported the sad case of a chimpanzee mother who lost her daughter, before now publishing about a second unusual case: the death of an adult chimpanzee named Thomas.
Masya inspects the face of her deceased daughter carefully. A single group member pays attention briefly, before returning to continue with the order of the day. (Click here for movie clip.)
The respective chimpanzees had been observed before in their response to deceased group members, but never to the death of an adult individual who has established meaningful social bonds with others. When an adult chimpanzee named Thomas passed away, almost the entire group gathered around him and looked silently at the body. This is unusual because chimpanzees are generally restless in large groups and therefore prefer to stay in small subgroups, but this event brought everyone together in a way that researchers had never seen before.
Group members gather around the body; they sit idly, without any significant events occurring; at times one member specifically inspects the body.
Selective “mourning” behaviour
Earlier observations showed that primate mothers sometimes carry their deceased offspring with them for prolonged times, or even go through a phase where they slowly learn that their offspring is actually dead (read here). In the previously observed case, only the mother inspected the body; the other chimpanzees only briefly showed interest before leaving the body again. However, the new observations show that when such a tragic event relates to a socially mature individual, the reactions of the other chimpanzees are more elaborate and also more specific. Besides the fact that almost the entire group gathered at the dead body, there were some striking behaviours observed. For instance, the adult male named Pan, who had always taken care of the deceased chimpanzee (Pan had adopted Thomas when Thomas’ mother died, which is quite remarkable in itself), strongly responded by frequently inspecting the body and chasing off a mischievous youngster who touched the body. "Pan always protected Thomas, and he seemed to exhibit the same care over the dead body of Thomas," said van Leeuwen, who has been closely involved in the study of this group of chimpanzees since 2007.
Noel (surrogate mother) uses grass to clean the deceased's teeth, while her daughter Nina, a loyal playmate of the deceased, is intently watching.
Care for the deceased
The researchers also observed how a female (Noel) – who had taken up the role as surrogate mother for Thomas after his own mother died – thoroughly inspected and even cleaned the body with attentive care. "Noel refused to be distracted by caregivers who offered food to lure the chimpanzees away... Instead, she stayed near Thomas' body and cleaned his teeth with dried pieces of grass," said van Leeuwen.
"These observations show that chimpanzees’ reactions to death are determined by social characteristics of the deceased, and that their selectivity is related to how well they got along with the deceased. Such observations remind us of the extent to which our sociality, including our care for the dead, has its roots in our evolutionary history."
Link to the publication:
Link to the videos as reported by the BBC and Dutch newspaper NRC: