The first ever witnessed case of a newborn wild chimpanzee being taken from the mother and subsequently eaten was published by researchers from Japan this week in the American Journal of Physical Anthropology. The authors explain that this most likely occurred because the pregnant chimpanzee did not go on “maternity leave”, a period near the time of birth that the mother chimpanzee hides and gives birth alone.

Just a matter of seconds after the mother, Devota, gave birth and before she could touch her newborn, an adult male chimpanzee, Darwin, picked up the infant and took it into the bush. The researchers therefore couldn’t confirm if it was a live or still birth or the sex of the infant. Darwin and other members of the group were subsequently seen eating the newborn. At the time of the incident in 2014, there were about 60 members in the group, with 20 adult females and 10 adult males.

Photo of Darwin with the infant that was subsequently cannibalised (Nishie and Nakamura 2018).

There have been 45 sightings of infanticide in wild chimpanzee groups in six different populations, but never around the time of birth. This incident occurred in group “M” from the Mahale Mountains National Park in Tanzania, which have been studied since 1968. The authors found clear evidence for maternity leave from data from their daily attendance records between 1990 and 2010 with a total of 94 births to 36 females.

Infanticide perpetrated by males has been observed in many primate species and is usually explained as being a male reproductive strategy, whereby males increase their chance of fathering an infant by killing unrelated infants, and results in the mothers becoming fertile again sooner after birth.

The authors propose explanations for why Devota gave birth without “maternity leave”: 1) the baby was preterm and was therefore “not expected”; 2) it was her first pregnancy and had not learned the behaviour of “maternity leave”; and 3) she felt safe in the group as she may have copulated with a number of males around the time of conception of the infant.