Recently at Discovery News we told you how chimpanzees confront death. They do so in ways that are very similar to our behavior toward dying friends and relatives.
On the surface, it might at first seem that chimpanzee mothers break from those noted similarities. When their offspring die as infants, the mothers will continue to carry and groom the dead bodies until the mothers are able to gradually let go of them. By that time, the infant's body has usually mummified.
(Chimpanzee infant's mummified body shortly after it was released by its mother; Credit: Tatyana Humle)
The behavior likely mirrors, at least to some extent, the biophysical reaction of human mothers when they too lose young sons or daughters. Right after birth, the mother's body is hormonally, and in many other ways, ready to care for the infant. Even after a baby dies, the physical connection can take time to adjust. This isn't even taking into account the emotional bond.
Chimpanzees go through this adjustment period in a very literal way, by continuing to provide care for their deceased infants.
(Credit: Tatyana Humle)
I recently interviewed University of Oxford zoologist Dora Biro, who witnessed the chimpanzee behavior in the forests surrounding Bossou, Guinea. We often cannot include all of this information in our stories and video segments, so I'd like to share her comments with you now.
JV: Is it possible that the mothers did not fully understand their offspring were dead?
Biro: Yes – this is one of the key questions that our observations
raise, I think. It's probably fair to say that it's very difficult to
make a claim either way (ie. clearly for or clearly against their
understanding that the infants were dead). As observers in the field,
we only have access to behavior, not to internal mental states – which
makes it very difficult to speculate on the real extent of the chimp's
understanding. They did certainly seem to understand that the infants
were immobile and unable to cling by themselves (clinging is something
that all chimp infants, even newborns, are very good at – the mother
usually does not have to support them at all during travel) – this is
why they had to come up with special ways of carrying the bodies that we
don't see with normal live infants (although as the Current Biology paper mentions,
mothers of disabled infants also adjust their way of carrying to
accommodate the needs of the infant). But as for whether they understood
from the start that this meant that the infants were dead, that they
would never come back to life again – or whether they gradually, with
time, came to understand it – or even whether they never fully
understood… is extremely hard to say.
you think, where the mothers did clearly realize that their infants had
died? If so, when did that happen?
Biro: No, I don't think we can clearly pinpoint such a time. Having said
that, we did not actually observe the exact moment of death in the case
of either infant, so do not know how the mothers reacted at the time
(and it's possible that we would have seen some specific reaction,
perhaps distress, anger, or fear, that would have indicated that they
grasped, at that point, the transition between life and death).
(Chimpanzee mother climbs a tree for food, with her mummified infant's body still in tow; Credit: Tatyana Humle)
unusual appearance" didn't repel the other chimps. If a healthy chimp
smells or looks abnormal, due to an accident, illness or something else,
do the chimps usually still accept that individual, if he or she was
formerly in their troop? It sounds like mothers will accept handicapped
infants, but I'm wondering about behavior towards previously healthy
individuals who have changed. Among my cats, for example, if one has a
surgical procedure and smells like medicine, the other cats will become
aggressive and then stay far away.
Biro: Interesting question. I think in the case of your cats, the very
"unnatural" (for them maybe "human") smell of the medicine may be what
scares them off. Among wild chimps, injuries and illnesses are quite
common (unlike a surgical procedure in cats) so they will encounter such
individuals often, and these individuals do not get ostracized. For
example, we've seen a young chimp cradling his injured, bleeding finger -
in that case too, the responses of other group members basically
amounted to curiosity rather than any form of aggression or avoidance.
towards deceased infants?
Biro: This is a really hard (and sensitive) question. Certainly in
humans the loss of loved ones is an immensely painful experience, and
the loss of a child perhaps almost inconceivably so. (This is why i am
slightly wary of direct comparisons). We can likely assume an emotional
response in the chimpanzee mothers too as a result of the loss of their
infants, but obviously the carrying of the infants' remains is not
something that happens in humans. At the same time, we probably
experience feelings of a "refusal to let go" even if we don't act on it
in the same way as these mothers did. And yet, we might hold on to
objects that remind us of the deceased person instead – we feel simply
unable to throw them away, often for long periods after death – and
these can be extremely emotive for us.
Another important point, important comparison, is perhaps in terms of
the extremely strong mother-infant bond that exists in chimpanzees.
Chimp newborns, much like humans, are completely helpless, and need
full-time care from the mother. This is why chimp mothers (and humans
too) have been shaped by natural selection to be very protective of
their infants – to look after them, defend them, feed them, protect them
at all times. The prolonged carrying may then be a by-product of this
extremely strong bond – the same force that keeps the mother looking
after the infant while it is alive can persist even beyond the infant's
(Credit: Oxford University, Dora Biro)
JV: How might studies such as yours shed
light on human behavior and attitudes toward death?
evolutionary reasons why – if we want to understand the evolutionary
origins of our own perception of death – we need to look first to our
Biro: Perhaps something about conservation – the community we studied is
extremely small, but it is one of the longest-running chimpanzee field
sites in Africa, and has over the years contributed with a lot of
interesting observations to our knowledge of wild chimpanzee behavior.
Such communities are therefore extremely precious. The disease that
killed these infants (as well as three other community members – in
total, over a quarter of this small population) possibly originated in
humans, and had a huge impact on the group in terms of its numbers and