Chimps have been filmed tending to the dead for the first time in a reserve in Zambia. An adult female was seen cleaning the teeth of her adopted son with a stiff piece of grass.

The female, named Noel and aged 33, had been born in the wild but was living in the Chimfunshi Wildlife Orphanage Trust. She was seen grooming the dead body of a younger male, named Thomas, whom she had adopted after his mother's death, according to a study published in the journal Scientific Reports. Thomas is thought to have died from lung infections, an autopsy revealed.

More from IBTimes UK

"Noel approached Thomas' body, sat down close to his head, turned her upper body sideways to select a hard piece of grass, put the grass in her mouth, and opened Thomas' mouth with both of her hands," write the study authors, led by Edwin van Leeuwen of the Max Planck Institute for Psycholinguistics in the Netherlands.

Noel then put the piece of grass in her teeth to explore his teeth with her thumbs, before picking up the grass again.

"After three seconds, she took the grass out of her mouth with her right hand, while maintaining a focused grip on Thomas' mouth with her left hand, and started to meticulously poke the grass in the same dental area as where her thumbs had been."

The authors suggest that this behaviour in chimps could shed light on the origins of death rituals in humans. However, of the University of Geneva, Switzerland, cautions that this behaviour doesn't prove that chimps are practising death rituals as it's not clear whether Noel knew that Thomas was dead.

"We simply do not know if and how much chimps understand about death," Gruber told the New Scientist.

Chimp death ritual
Chimpanzees performing what is thought to be a death ritual involving cleaning the deceased's teeth. Edwin J. C. van Leeuwen et al, "Tool use for corpse cleaning in chimpanzees", Scientific Reports 7, Article number: 44091 2017 doi:10.1038/srep44091

"In other words, it is unclear whether this is 'corpse cleaning', or simply 'social cleaning'. But certainly, it adds on behavioural descriptions of unusual behaviour displayed by chimps when they face the death of one of their species."

This is not the first time that chimps have been filmed interacting with a dead body of a member of the group. In January scientists published a film of a group of chimpanzees attacking and eating the body of a former alpha male of the group after he had been killed.