Monday, May 30, 2011

Death and Grieving As Witnessed in Monkeys and Apes

There is nothing sadder than a parent mourning an infant.  Such experience is not limited to humans. Non human primates (as well as other animals) mourn their dead family members and friends.
Or at least they do show sign of sadness, grief and stress related to the death of a companion.

In "Baboon Metaphysics, The Evolution of a Social Mind" Dorothy L. Cheney and Robert M. Seyfarth write about the theory of mind in baboons, the rudiments of consciousness and self-awareness.
They describe the social life of baboons and how each individual acquires and constantly updates their knowledge about individuals' status and ranks within the group and talk about how female baboons react to loss: "The greatest stressors affecting female baboons are unpredictable events over which they have little control: predator attacks and infanticide." They go on to explain how female baboons cope by enlarging their social network, increasing their grooming activities and thereby lowering their glucocorticoid levels.  They write: "When her infant dies, a female baboon will often continue to carry the body for as many as 10 more days, cleaning the corpse of maggots and brushing flies away from it.  As the corpse decays and mummifies, she begins to leave the body for increasing lengths of time before finally abandonning it.  It is as if the mother continues to respond to the corpse of her infant even after it has lost all resemblance to a baboon." They then explain that other group members seem to cease seeing the infant as a living entity, they don't grunt when they approach it as they would if the infant were alive, however "they appear to recognize that the corpse still belongs to the mother. (...) When the mother moves away from the body, other group members grunt to her, and a close relative or male friend often guards the body until she returns."

Several accounts of grief in apes have been reported over the years.  In a paper published in 1879 and entitled "Grief in the Chimpanzee" naturalist Arthur E. Brown reports the behavior of a chimpanzee at the Philadelphia zoo: "After the death of the female, which took place early in the morning, the remaining one made many attempts to rouse her, and when he found this to be impossible his rage and grief were painful to witness.  Tearing the hair, or rather snatching at the short hair on his head, was always one of his common expressions of extreme anger, and was now largely indulged in, but the ordinary yell of rage which he set up at first, finally changed to a cry which the keeper of the animals assures me he had never heard before, and which would be most nearly represented as hah-ah-ah-ah, uttered somewhat under the breath, and with a plaintive sound like a moan.  With this he made repeated efforts to arouse her, lifting up her head and hands, pushing her violently and rolling her over." Brown continues on by describing how the lonely chimpanzee continued to grieve and became more attached to his keeper, and exhibited what would be described today as signs of separation anxiety each time the keeper left the enclosure.

In "Visions of Caliban, Chimpanzees and People" Jane Goodall and Dale Peterson talk about Flint, a male chimpanzee who lost his mother when he was eight years old and therefore capable of caring of himself.  "He just seemed to give up, and in the state of what we can describe only as grief, showing signs of clinical depression like grieving human children, he didn't want to eat, he didn't want to interact with the others, and, with his immune system weakened, he died within a short time of losing his mother."

These reports demonstrate that there is awareness of loss, kinship and emotional attachment to some individuals within a group.  It does not prove that non-human primates have knowledge of death or any understanding of it, but they seem to be affected by it somewhat similar to the way humans are affected by it.


National Geographic just published the pictures of a grieving gorilla mother in the Virunga National Park.
 
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