Chimps Mourn Deaths in the Family, Studies Find

(April 26) -- Chimpanzees have long been known to make tools, show empathy and cooperate with each other. Now scientific research is raising an intriguing question: Do chimps mourn their dead?

In two studies released today, scientists document the moving reaction of chimpanzees to the death of a comrade or close relative -- behavior that is rarely observed in either the wild or captivity. The cases join a growing number of reports of wild animals, from elephants to dolphins, that display what seems to be grief over a death. The chimps' behavior is likely to feed the debate over whether animals feel emotions and, if they do, how humans can find out.

In species like primates and whales, "I wouldn't be surprised if (there were) some degree of death awareness which is more advanced than many people would attribute to nonhumans," James Anderson of Scotland's University of Stirling, author of the new report on captive chimps, told AOL News.

Certainly to the nonscientist, the actions of the chimps seem driven by bereavement similar to our own. The first study describes two chimp mothers living in the forests of Guinea. Each lost her baby to a respiratory infection in 2003. For weeks, even months, the mothers carried the tiny bodies everywhere. They groomed their dead infants' fur, took the babies into their night nests and chased away approaching flies. (The video below shows a mother chimp shooing flies from her dead infant.)

It was "an unbelievably sad sight," Dora Biro of Oxford University, the author of the study, said in an interview. The mothers' behavior reflects "the very, very strong mother-infant bond that exists in chimps. ... What's amazing is this bond seems to last even beyond the infant's lifetime."

The second case also involved a mother and child. In 2008, Pansy, an elderly chimp at Blair Drummond Safari Park in Scotland, spent her final hours with the three other chimps she lived with, who groomed and stroked her. After Pansy's death, her grown daughter Rosie spent the night next to her mother's body.

The next day Rosie and the other two remaining chimps, normally noisy and boisterous, maintained a silence that was "eerie," head keeper Alasdair Gillies said. "I can't say ... from a scientific point of view" that they were mourning, "but the feeling you had was that you were in a group of mourning animals."

The video below shows three adult chimps attending to a dying chimp.


Other species that react strongly to death of kin or companions:

• Dolphins. Scientists in 2007 witnessed a bottlenose dolphin mother repeatedly pushing her dead calf to the water's surface over the course of two days. She emitted mournful cries while touching the calf with her flippers and beak. It was "quite clear" that the mother was emotional, said one of the scientists who witnessed the episode, Joan Gonzalvo of the Tethys Research Institute.
• African elephants. When a matriarch named Echo died in a national park in Kenya last year, her daughter Enid slept next to her mother's body for a number of nights. A 2006 study showed that elephants take a keen interest in elephant skulls and ivory, touching them with their trunks and feet.
• Bonobos, which look like small chimps. When a young male at a refuge for orphaned bonobos died, the others tried to keep human staffers from taking the body away, even when threatened with a dart gun, says Brian Hare of Duke University.

Scientists, including those who wrote the new studies, caution that it's all too easy for humans to project their own emotions onto animals. Perhaps there are alternate explanations for some of the behaviors that at first glance seem so touching, according to Clive Wynne of the University of Florida.

For example, Wynne says, perhaps the mother chimps who held onto their babies couldn't tell that the babies had died -- a scenario that Biro said is quite realistic. Or because a chimp baby is such an investment of energy and time for a mother, she is driven to keep trying to care for it in case it is not really dead.

Wynne believes that animals feel emotions, but "there is a whole kind of anthropomorphic feeling people project onto animals," he told AOL News. "Whatever the emotional life of other species is, it's very different from our own." He and others advocate experiments to test whether animals truly mourn their dead.

At least one such experiment has already been done, with intriguing results. Researchers found that baboons who lost a close relative showed spikes in the hormone cortisol, which is released in response to stress -- and which also shoots up in bereaved humans.

"Are they mourning and grieving?" Hare said. "I don't know. But they're very upset."

Both new papers are in Tuesday's issue of Current Biology.