Primate moms carry their dead babies with them. Scientists say it may prove they grieve like humans do.

·2 min read

Some primates may grieve dead infants by carrying their corpses with them, sometimes for months, according to a study examining mothers' responses to death among 50 primate species.

The study, published Wednesday in Proceedings of the Royal Society B: Biological Sciences, found "infant corpse carrying" behavior among many primate species, including gorillas, chimpanzees, macaques and baboons.

While nonhuman primates respond to death in a number of ways, infant corpse carrying is among the most frequently reported, according to the study.

Scientists have been unable to determine a clear explanation for the behavior, "especially considering that it is costly and provides no benefit for them," according to study co-author Elisa Fernández Fueyo's website.

Researchers at University College London compiled a database of 509 cases across 50 primate species of mothers' responses to infant deaths. About 80% of the species studied performed infant corpse carrying behavior.

Younger mothers were more likely to carry their dead baby, according to the study. Researchers say older primates may have already learned when to recognize if their baby is dead and may be more able to break their bond with the baby as a result, suggesting that primates are able to attain an awareness of death over time.

"While there is debate among scientists around whether primates are aware of death, this new study suggests that primate mothers may possess an awareness — or be able to learn about death over time," according to a Wednesday statement from University College London.

"Our study indicates that primates may be able to learn about death in similar ways to humans: it might take experience to understand that death results in a long-lasting 'cessation of function,' which is one of the concepts of death that humans have," study co-author Alecia Carter said in the statement. "What we don’t know, and maybe will never know, is whether primates can understand that death is universal, that all animals – including themselves – will die."

In addition to the age of the mother, the study found two other factors that influenced whether the mother would carry her dead baby. Infant corpse carrying was more common when the infant's death was non-traumatic, through illness or stillbirth, than if it was traumatic, through a predator attack or accident. The age of the baby when it died is also a factor, with mothers carrying younger babies for longer.

The study adds to existing knowledge about how non-human primates process grief and shows "how strong and important maternal bonds are for primates," Carter said.

Despite the findings, Fueyo said more research is needed to determine how much primate behaviors resembled human grief.

“We found that bonds, particularly the mother-infant bond, possibly drive primates’ responses to death," Fueyo said. "Because of our shared evolutionary history, human social bonds are similar in many ways to those of non-human primates"

Contact News Now Reporter Christine Fernando at cfernando@usatoday.com or follow her on Twitter at @christinetfern.

This article originally appeared on USA TODAY: Primate mothers may grieve by carrying dead infants, study suggests