Are primates capable of grieving? Do they know what death is?
Animals do the most amazing things. Read about them in this series by Janaki Lenin.
An animal would have to recognise the irreversibility of death to grieve for a dead group or family member. Are primates capable of grieving? Do they know what death is?
Many female primates, from bonnet macaques to gorillas, carry the corpses of their dead infants for weeks. In some cases, the bodies reach a state of mummification before the mothers abandon them.
In 2011, Peter Fashing of California State University, Fullerton, US, and his colleagues reviewed 14 instances of gelada mothers carrying the corpses of their infants. Not only mothers, even juvenile females groomed and carried the dead bodies. In one case, a female of another group tended to the remains. Even though the corpses smelled foul, the rest of the group didn’t avoid the female carrying them. Most mothers abandoned the remains after hormonal changes stop lactation and start the ovarian cycle. But one gelada mother continued to carry the mummified corpse of her offspring even while mating. The authors surmise two possible reasons for this behaviour – the delayed decomposition of corpses because of the cold conditions may prolong the geladas’ interest in them and such responses to death may originate in ancient primates.
Such instances of mothers carrying the remains of their infants are very visible and offer opportunities for primatologists to study primates’ response to the death of young. Many species are social animals, eating, playing, grooming, and sleeping together. Within a group, individuals bond, spending more time with each other. How would the death of an adult affect the others? Opportunities to study their reactions to the deaths of companions and fellow group mates are fewer.
Edwin van Leeuwen of St. Andrews University, Scotland, and colleagues from the Chimfunshi Wildlife Orphanage Trust, Zambia, and Katherine Cronin of Chicago’s Lincoln Park Zoo, U.S., published one of the few instances of a chimpanzee group’s reaction to the death of a member.
In May 2010, Thomas, a nine-year-old chimpanzee, had been missing for two days before he was discovered lying dead. The necropsy said he died of a bacterial and viral infection had made breathing difficult. Since the keepers hadn’t seen the body lying in that spot earlier, they concluded that it had been dragged from elsewhere. They recorded how the rest of the group reacted to the body with a video camera.
Although the orphanage provides sanctuary to chimpanzees rescued from illegal trade, a majority of a 43-member group called ‘Group 2’ by staff were born in captivity. Thomas was born to a wild-caught mother. His group roams through a 160-acre outdoor enclosure of dense forest.
According to the staff, Thomas was social, parked by the door of the indoor holding facility. He and his companion Pan, another male chimpanzee, called, greeted, and played with any passing chimp. They paid particular attention to adult females.
About half the group gathered around Thomas’ body. A group can splinter into sub-groups and forage in different areas. So the rest may have been elsewhere within the large enclosure and probably didn’t know of his death.
Within four minutes of the body’s discovery, Pan, the dead chimp’s buddy, picked up a tree branch and lunged towards the body, sending the others screaming and scurrying out of the way. He hit a female, or at least hit the ground near her, and she chased him into the forest. He returned, forcing his way close to the body every few minutes to examine it once again. About 15 minutes later, he ran towards Thomas’ body, pulling tree branches, and disappeared from the scene while chasing a female.
Ignoring the caretakers’ calls to feed, Violet, the dominant female, who had been watching Pan, stood up on her hind legs and began screaming. She rocked back and forth as she walked slowly towards the body. When she was close enough, she hit it hard before running away.
Except for these dramatic interludes, most of the others gathered around the body and sat quietly, while some inspected it. Edwin van Leeuwen, the main author of the study, says sitting quietly is not typical chimpanzee behaviour.
After Violet’s departure, Noel, another adult female, cleaned the dead chimp’s teeth with a grass stem.
There are no records of chimps cleaning the teeth of dead infants. “I think it’s quite special. Especially given that Noel preferred doing this over getting lots of food on the other side of the enclosure,” says van Leeuwen.
Twenty minutes after discovering Thomas’ body, the caretakers removed it.