Thread by @corvidresearch

So for the past week one of our southern resident orca whales has been carrying around her dead calf. This is heartbreaking for a number of reasons including that our southern resident orcas are endangered. time.com/5353745/orca-d…

Given the mother’s response, there’s been ongoing coverage with lots of headlines including words like grief and mourning, and many of the whale researchers have been using these words too.

Let me be clear: I am not here to say that they’re wrong, or that non-human animals can’t feel sad. There’s nothing about orca societies or brains that would preclude high emotional intelligence and in fact, just like it has for humans, it may contribute to their success.

But since I know the literature on what wild animals do around their dead pretty well, I want to help put this event into context, and offer some of the questions that these accounts make me ask.

Across the animal kingdom dead infant transport is incredibly rare, but in a few groups of animals it’s not uncommon. There are dozens of accounts in dolphins (bottlenosed, rough-toothed etc.), primates, as well as accounts in manatees and one in dingos.

The fast majority of these accounts are documented observations, meaning scientists saw this happening and documented it rather than ran some kind of controlled experiment on it.

What that means is that we have no idea how common this behavior is across most species. The one exception is a study on Japanese macaques that found that over a 10yr period, 10% of infants were carried postmortem by their mother. jstage.jst.go.jp/article/ase/11…

Most abandoned the bodies after a day but it could go on as a long as 17. Interestingly, young, first time mothers carried their dead infants more often than older mothers, but this did not reach significance. Again, this kind of info is not available for any other species.

Other primates that have been documented to carry their young include: Mountain gorillas, chimpanzees, bonobos, orangutans, Taihangshan macaques, Tonkean macaque, gelada baboons, Hanuman langurs, Yunnan snub-nosed monkey, and capuchins.

In some cases the infants are carried far beyond the point that they have any resemblance to living young. In one case a chimpanzee carried her dead infant for 68 days.

It's worth noting that it's not always mothers doing this. In Barbary macaques males have been documented transporting and grooming dead infants. One account in mountain gorillas found that an unrelated female carried a dead infant (possibly after being the one to kill it)

So what do scientists say in response to these behaviors, and why is it less clear, and more complicated, than simply saying "they're obviously sad"? Well first, our job as scientists is to not over or under-interpret animal behavior.

Our job is to use empirical evidence to inform our explanation of the natural world. With so few quantitative studies on this behavior it's impossible to offer a well informed explanation and "they're sad because I feel like they're sad" is not sufficient.

So what explanations, even speculative ones, have been offered? Maternal hormones, learning to mother, learning about death, grief, unawareness of death, wait and see strategy (maybe it recovers?), signals maternal dedication (hey future mates, look at me, I'm a good momma)

social learning, stress reduction, and social facilitation. There are probably others I haven't come across too. Ok so scientists are of course going to be unwilling to rush to conclusions about grief, but what about the actual behaviors suggests that this story is complicated?

Well first, it doesn't happen often. What's different about the mothers that don't engage in this behavior? If sadness drives this behavior, as these mothers less sad? Or expressing it differently?

In the case of the macaques, why wouldn't older young garner more attention, since they're had longer to bond with their mother? Then there's the observation that mothers sometimes eat the babies they're carrying. And not like they carried it and then finally ate it

but they ate it a little bit at a time and continue to carry it around. During this time they may even be expressing other care-taking behaviors like grooming. In one case a bonobo groomed her dead infant and then as soon as she finished, she ate it. onlinelibrary.wiley.com/doi/pdf/10.100…

So far (and gosh, hats off to you is you're still here), I've spent most of this thread on primates because we know more about these behaviors in them than we do in marine mammals. But let's return now to cetaceans (whales, dolphins and porpoises).

Interactions with dead infants in this group are less varied than they are with primates. All the accounts I've read describe basically describe mothers using their dorsal fins or mouths to carry dead young or bring them to the surface. I don't know of cases involving males.

Like primates, the corpses can vary in freshness and age. One interesting difference with cetaceans is that there are multiple accounts of them carrying or supporting the dead bodies of other species such as other whales, turtles, sea otters or sharks.

Perhaps b/c of the more consistent behaviors in cetaceans I more often see words like mourning or grief in the concluding remarks of those papers, than in ones about primates. Which, again, I don't mean to suggest isn't happening or possible.

But what does it mean then when they attack or attempt intercourse with dead adults? Or what implications are there when our southern resident orcas stalk and kill (mostly baby) Dall and harbor porpoise just to play with their bodies? Can you posses grief without empathy?

I don't ask to be rhetorical, to me it's an interesting question. In children, if one developed far later than the other that might suggest they are different mechanisms, but in fact both empathy and the ability to conceptualize death and express grief start around the age of 2.

So for me the jury is still out. I know neither if other animals can feel grief or malice. In the mean time my heart will continue to ache for the mother that lost her calf and my brain will continue to mull the implications of what it all means.

I should add that this of course not a dichotomy. The options are not limited to: they either feel things exactly as I do or feel nothing at all. But the catalyst for this thread was the use of words like “mourning” so I focused on that end of the emotional spectrum.

I also want to make clear, because it seems some folks think I haven’t noticed this...that humans of course can both mourn and intentionally cause harm. That those can coexist is not strange.

I brought that up because there seems to be more eagerness to accepting grief among animals than these other complex, but dark emotions. Unless of course we’re using them as an excuse to be mad at our dogs (they know better but did this upsetting thing to get back at me” etc.) 🙄

Also...Apologies for the sloppy writing. This thread took shape over the course of hours while being multitasked with other demands. Then I sent it off without proofreading so I didn’t miss my bus. But hey, that’s how you know it’s a genuine Swift thread 😂

Last thing...if you want to learn more about this topic please check out the following papers which are all fascinating!

cell.com/current-biolog…

onlinelibrary.wiley.com/doi/abs/10.100…

scholar.google.com/scholar?hl=en&…

researchgate.net/profile/Dan_Ke…

I want to give a special shout out to @claireFIWatson1 whose new paper was not only an immense source of information for this thread, but appears in the same issue of Phil Trans B that my recent pub does! rstb.royalsocietypublishing.org/content/373/17…