(Phys.org)—A trio of researchers from the U.K., the Netherlands and the U.S. has filmed a grown female chimpanzee cleaning her son's teeth after he died. In their paper published in the journal Scientific Reports, Edwin van Leeuwen, Katherine Cronin and Daniel Haun offer a description of the circumstances under which they shot the video and their ideas on why the female was behaving the way she was.
Chimps have been observed cleaning one another's teeth on multiple occasions. Besides serving as a hygienic practice, it is believed to be a bonding ritual as it typically occurs between those that are seen to be close to one another. Chimps have also been observed brushing the fur of dead group members. But never before has a chimp been observed tending to the teeth of a deceased member of their group.
The researchers report that the chimps involved were living in the wild at Chimfunshi Wildlife Orphanage Trust in Zambia and that the deceased young male chimp appeared to have died due to a lung infection. The deceased chimp had been orphaned four years before and was subsequently adopted by the older female. They report also that prior to the teeth cleaning, the older chimp had cradled her adopted son's head in her hands as she examined his teeth. She then removed a piece of straw from her mouth and began using it to remove bits of debris from between the teeth of the deceased chimp. Another younger female chimp, the daughter of the older female sat nearby watching. The researchers note that as the older chimp removed the dental debris, she placed it in her own mouth, perhaps in an attempt to understand why her son had died.
It is impossible to know the motives of the older chimp, of course, though it is easy to apply human emotions to the scene shown in the video—it looks like a grieving mother. But scientists have not been able to prove that chimps feel grief, or a similar emotion. They also have no idea to what degree chimps understand death. The researchers suggest that the isolated activities of the chimp in the video might offer some clues as to how mortuary rituals began in humans.
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More information: Edwin J. C. van Leeuwen et al. Tool use for corpse cleaning in chimpanzees, Scientific Reports (2017). DOI: 10.1038/srep44091
For the first time, chimpanzees have been observed using tools to clean the corpse of a deceased group member. A female chimpanzee sat down at the dead body of a young male, selected a firm stem of grass, and started to intently remove debris from his teeth. This report contributes novel behaviour to the chimpanzee's ethogram, and highlights how crucial information for reconstructing the evolutionary origins of human mortuary practices may be missed by refraining from developing adequate observation techniques to capture non-human animals' death responses.