A male chimpanzee has been observed snatching a seconds-old newborn then eating it. This behavior has never before been documented by scientists, who say it could explain why female chimpanzees normally hide themselves away during the late stages of pregnancy.

In December 2014, scientists were studying a group of chimpanzees at Mahale Mountains in Tanzania. On a rainy day in the mountains, one chimpanzee named Devota suddenly gave birth in front of the group. Until that moment, the scientists didn’t even know that she was pregnant. In a flash, an older male named Darwin ran to her and snatched the baby away. It was so sudden that the mother didn’t even have a chance to hold her infant.

The male ran away from the group, clutching the infant. The researchers weren’t able to see if the baby had been born dead or if Darwin killed it. Either way, he then climbed a tree and consumed most of the infant’s body. The researchers could not tell whether the infant was alive when Darwin ate it.

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Male_Chimp_Holding_Dead_Baby

Nishie & Nakamura, Am J Phys Anthropol (2017)

The observation appeared in a case study published in The American Journal of Physical Anthropology in September. The researchers were studying the lengths of “maternity leaves” among chimps. Typically, female chimps leave their family group when they are ready to give birth and they deliver alone. The researchers found that females who take a break from the group for reasons other than pregnancy spend less time away than those who leave specifically to deliver.

Cannibalizing an infant is a bad idea. “Infanticide and cannibalism impose large reproductive costs on females and fathers of infants, so theoretically, effective counter-strategies should evolve to avoid such costs,” wrote Hitonaru Nishie, an anthropology researcher at Kyoto University, in an email to Newsweek. Nishie was one of the authors of the study.

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And such behavior is extremely rare among these animals. “Cannibalism is extremely widespread across nature, but it’s pretty rare in primates, chimps notwithstanding,” Bill Schutt, author of Cannibalism: A Perfectly Natural History, told Newsweek. He explained that chimpanzees have been occasionally observed cannibalizing infants of other groups, but not their own. “But there’s always aberrant behavior.”

Yet eating one's own species can have some survival-driven motives, Schutt continued. A male might want to kill an infant in his own group to make the female ready to mate again. A female with a someone else’s baby won’t be willing to mate, meaning she’ll spend time raising someone else’s offspring instead of yours.

The unexpected cannibalism event left several questions unanswered. The researchers were not able to obtain DNA samples from Darwin and the baby to determine if they were related. Researchers also questioned the nutritional value of the baby’s body, as Darwin had severe diarrhea right after consuming it. They also weren’t sure why Devota had the baby in front of the others, although they speculate that she might have been a first-time-mom and not known any better.

Darwin’s consumption of his group-mate’s infant may have been a rare occurrence. However, it does give insight into why females may take leave during their pregnancy—to protect their babies from being eaten.

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