Chimpanzee and bonobo mothers carry dead offspring for days, but does this prove they understand death?
Desperate mothers, not wanting to say goodbye, carry the bodies of their children who have already died. We are not talking about human mothers, but chimpanzee mothers.
The behavior is common and often observed, both in chimpanzees and bonobos, and has led scientists to question whether it is mourning, which implies a notion of death, or the opposite: an automatic prolongation of maternal care, without a clear understanding of the irreversibility of death?
A new study, not yet peer-reviewed, analyzed 83 published cases of “calf cadaver transport” (ICC). Chimpanzees and bonobos belong to the genus Pan and are our closest living relatives, which is why their behavior is often used to discuss which cognitive abilities they can share with humans, explains .
The authors of the work at bioRxiv argue that, in most of the situations described, the transport of the body does not, in itself, require a “complete” notion of death as an irreversible biological state. Instead, the phenomenon may result mainly from a rooted standard of care: the mother continues to act as if the calf were still alive, because the routine and the maternal bond have been strongly reinforced over time.
The study points to several associations that support this last hypothesis. One of the main ones is the relationship between the duration of ICC and the age of the offspring at the time of death.
On average, mothers would carry older offspring for longer than newborns — the longer the mother spent caring for the offspring, the stronger the bond tends to be and the more “automatic” the set of care behaviors becomes, which makes it more difficult to interrupt them immediately, even after death.
Another association observed concerns the interval between births in the group. In populations with larger reproductive spacings, the duration of the ICC would, in general, be longer.
A how the baby dies also appears to influence the pattern. ICC tends to last longer when death occurs from disease than when it results from infanticide committed by adult males. One possible interpretation is that, in the absence of a violent event, the death may be “more ambiguous” and less perceptible to the mother. But the authors give another explanation: the social risk. After infanticide, keeping the body can increase tension with males and expose the female to further aggression, making faster abandonment a risk reduction strategy.
But then there are cases that seem inexplicable in which, for example, mothers transported corpses for so long that they mummified. For the authors, even this scenario can be compatible with an explanation based on habits of care and bonding, without necessarily implying a mental representation of death as “final”.
Remember that there are records of other species — even marine ones — with similar “mourning” behavior.
There are reports in India of covering or “burying” the bodies of infants and of Japanese macaques maintaining caring interactions with dead companions. In the ocean, one of the most popular images was that of an orca that, in 2018, carried its dead calf for 17 days; the same animal was again observed in similar behavior after another loss in early 2025.
And of course, we cannot forget the reaction of the famous gorilla Koko, trained in American Sign Language, who was able to express sadness for the death of his pet kitten, All Ball, and mourned the passing of his friend Robin Williams. And, when asked where gorillas go after death, she said: “Comfortable hole, goodbye.” Or the case of Mama, the chimpanzee who, it is said, lay down to die, but smiled once again when she saw her former friend.
