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Chimps Grieve Over Dead Relatives

26 April 2010 12:03 pm
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In November of 2008, a chimpanzee in her 50s known as Pansy became lethargic and obviously ill at the Blair Drummond Safari and Adventure Park in the United Kingdom. Three other adults, including Pansy's 20-year-old daughter Rosie, began tending to her, grooming her, and sleeping nearby instead of in their own nesting areas. Pansy continued to deteriorate over the next few weeks, until one day her breathing suddenly became erratic. During the 10 minutes before Pansy's death, the others groomed and caressed her constantly, and Rosie remained near her mother during the night. Keepers removed Pansy's body the next day, and the adult chimps remained unusually subdued for nearly a week.

In two new studies, published online today in Current Biology, researchers cite this and a case of chimp mothers carrying around their dead infants to support the idea that our closest evolutionary cousins share many humanlike responses to death, including mourning. The work offers some of the first clear evidence of grieving in animals other than humans, though we may consider some of the behaviors bizarre.

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A mother's loss. Vuavua, a chimpanzee mom, chases away flies circling the body of Veve, her dead infant, at Bossou, Guinea.
Credit: Dora Biro

Most animals show few signs of being disturbed when one of their fellows dies. For example, red deer used to hearing rifle shots will remain relatively impassive when another deer is shot dead by a hunter. One notable exception is the African elephant, which has often been observed engaging in empathetic and caring behavior toward dying members of its species. (In one such episode, observed by researchers in Kenya in 2003, an elderly elephant named Eleanor collapsed and was helped to her feet several times by other elephants before she died the following day. Her fellow elephants then kept an apparent vigil over her body for about a week, occasionally poking at her and lifting her legs and trunk.)

Researchers have long suspected that chimps and other apes might engage in similar behavior, but they very rarely observe the death of a chimp in the wild, says Richard Byrne, a psychologist at the University of St. Andrews in the United Kingdom. Zoos usually separate dying individuals from fellow chimps, he adds, making observations of their responses very difficult. In Pansy's case, zookeepers decided to allow the other chimps to stay with her as she died, while a research team, led by psychologist James Anderson of the nearby University of Stirling, observed their reactions.

In a second example of chimpanzee grieving, a research group led by Dora Biro, a zoologist at the University of Oxford in the U.K., observed two chimp mothers carrying the remains of their dead infants for weeks. The observations were made in the forests of Bossou, Guinea, where primatologists have been studying wild chimps for 3 decades. In 2003, an epidemic of respiratory disease broke out at Bossou, killing five chimps. Two were infants, 1-year-old Jimato and 2-year-old Veve. The mothers of the infants carried their dead bodies around on their backs for 68 and 19 days, respectively, even as they dried out and became mummified. They brushed flies away from the babies, groomed them regularly, and allowed other chimps—including other young animals—to poke at the bodies, lift their limbs, and even carry them around for short distances.

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Gone too soon. A young chimpanzee plays with the mummified corpse of the infant Jimato at Bossou, Guinea.
Credit: Dora Biro

In the case of Pansy, Anderson and his colleagues conclude that the other chimps reacted to her death in humanlike ways, experiencing grief and mourning. "Some of the behaviors appear strikingly similar to aspects of human responses to death and dying," Anderson says, adding that many researchers have considered such reactions to be unique to humans. Christophe Boesch, a primatologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, says that his team has observed similar behavior among chimps at Tai Forest in the Côte d'Ivoire and agrees that "we have certainly underestimated awareness of death in chimpanzees."

The Bossou study is more difficult to interpret, researchers say, because it is not clear whether the mothers realized that their infants were truly dead. "It's extremely difficult to make any claims either way," Biro says. "We only have access to behavior, not to internal mental states." But Byrne, who once observed a gorilla carry her dead baby around for 3 days in the mountains of Rwanda, points out that hospitals and doctors are increasingly giving the parents of a deceased infant the option of remaining with the body of their child for hours or even days before giving it up for burial, as a way of aiding the grieving process. Anderson hopes the Pansy episode will encourage zoos to do the same.

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