Placeholder Image

Subtitles section Play video

  • Whether we want to or not, humans spend a great deal of time

  • considering death.

  • And it's possible we've been doing so since shortly after homo sapiens

  • first began roaming the landscape.

  • After all, the first intentional human burial

  • is thought to have occurred around 100,000 years ago.

  • What might those early people have been thinking

  • as they took the time to dig into the earth,

  • deposit the body

  • and carefully cover it up again?

  • Were they trying to protect it from scavengers

  • or stymie the spread of disease?

  • Were they trying to honor the deceased?

  • Or did they just not want to have to look at a dead body?

  • Without the advent of a time machine,

  • we may never know for sure what those early people were thinking,

  • but one thing we do know is that humans are far from alone

  • in our attention towards the dead.

  • Like people, some animals,

  • including the corvids, the family of birds

  • that houses the crows, ravens, magpies and jays,

  • also seem to pay special attention to their dead.

  • In fact, the rituals of corvids may have acted as the inspiration

  • for our own.

  • After all, it was the raven that God sent down

  • to teach Cain how to bury his slain brother Abel.

  • But despite this clear recognition by early people that other animals

  • attend to their dead,

  • it's only fairly recently that science has really turned its attention

  • towards this phenomenon.

  • In fact, a formal name for this field -- comparative thanatology --

  • wasn't first introduced until 2016.

  • In this growing field, we are beginning to appreciate what a rich place

  • the natural world is with respect to how other animals interact with their dead,

  • and it's in this growing body of knowledge

  • that that time machine to our early ancestors might be possible.

  • So what are we learning in this growing field?

  • Well, right now we can split our understanding into two main groups.

  • In the first, we have animals that display stereotyped, predictable behaviors

  • towards their dead,

  • and for whom much of what we understand about them

  • comes from experimental studies.

  • This group includes things like the social insects --

  • bees and ants and termites --

  • and for all of these animals, colony hygiene is of critical importance,

  • and so as a result these animals display rigorous undertaking behaviors

  • in response to corpses.

  • For example, they may physically remove carcasses from the colony.

  • They may consume them.

  • They may even construct tombs.

  • We see similar hygiene-driven responses in some colony-living mammals.

  • Rats, for example, will reliably bury cage-mates

  • that have been dead for 48 hours.

  • In our other group, we have animals that display more variable,

  • perhaps more charismatic behaviors,

  • and for whom much of what we understand about them

  • comes from anecdotes

  • by scientists or other observers.

  • This is the animals whose death behaviors

  • I suspect might be more familiar to folks.

  • It includes organisms like elephants,

  • which are well-known for their attendance to their dead,

  • even in popular culture.

  • In fact, they're even known to be attracted

  • to the bones of their deceased.

  • It also includes animals like primates,

  • which display a wide variety of behaviors around their dead,

  • from grooming them

  • to prolonged attention towards them,

  • guarding them,

  • even the transportation of dead infants.

  • And that's actually a behavior we've seen in a number of animals,

  • like the dolphins for example.

  • You may remember the story of Tahlequah,

  • the orca in the resident J pod in the Puget Sound,

  • who during the summer of 2018

  • carried her dead calf

  • for an unprecedented 17 days.

  • Now, a story like that

  • is both heartbreaking and fascinating,

  • but it offers far more questions than it does answers.

  • For example, why did Tahlequah carry her calf

  • for such a long period of time?

  • Was she just that stricken with grief?

  • Was she more confused by her unresponsive infant?

  • Or is this behavior just less rare in orcas

  • than we currently understand it to be?

  • But for a variety of reasons,

  • it's difficult to do the kinds of experimental studies

  • in an animal like an orca, or many of these other large mammals,

  • that might elucidate those kinds of questions.

  • So instead, science is turning to an animal whose behaviors around death

  • we've been thinking about since BCE:

  • the crows.

  • Like insects and primates,

  • crows also seem to pay special attention to their dead.

  • Typically, this manifests as the discovering bird alarm calling,

  • like you can see in this photo,

  • followed by the recruitment of other birds to the area

  • to form what we call a mob.

  • But it can be a little different than that too.

  • For example, I've had people share with me seeing prolonged silent vigils by crows

  • in response to deceased or dying crows.

  • I've even had people tell me of witnessing crows place objects

  • like sticks and candy wrappers on or near the bodies of dead crows.

  • And this mix of observations puts these birds

  • in a really important place in our scheme,

  • because it suggests on the one hand they might be like the insects,

  • displaying these very predictable behaviors,

  • but on the other hand we have this handful of observations

  • that are more difficult to explain and feel a bit more like what we see

  • in some of the mammals like primates and elephants.

  • And like those animals, crows share an extremely large relative brain size

  • and the kinds of dynamic social lives that might invite more complexity

  • in how they respond to their dead.

  • So I wanted to try to understand what was going on

  • when crows encounter a dead crow,

  • and what this might teach us about the role of death in their world,

  • and possibly the worlds of other animals as well,

  • even those early versions of ourselves.

  • There's a number of different ways that we could explain

  • why crows might be attracted to their dead.

  • For example, maybe it's a social opportunity,

  • a way for them to explore why that individual died,

  • who they were

  • and what impact this is going to have on the neighborhood moving forward.

  • Maybe it's an expression of grief,

  • like our own contemporary funerals.

  • Or maybe it's a way that they learn about danger in their environment.

  • While all of those explanations are worth pursuing,

  • and certainly not mutually exclusive,

  • they're not all testable scientific questions.

  • But that idea that dead crows might act as cues of danger, that is.

  • So as a graduate student, I wanted to explore that question,

  • particularly with respect to two ideas.

  • The first was whether they might be able to learn new predators,

  • specifically people,

  • based on their association with dead crows.

  • And the second was if they might learn places

  • associated with where they find crow bodies.

  • So to do this, I would go out into some unsuspecting Seattle neighborhood

  • and I would start to feed a breeding pair of crows

  • over the course of three days,

  • and this provided a baseline

  • for how quickly the crows would come down to a food pile,

  • which, as you'll see in a minute, was really important.

  • Then, on the fourth day,

  • we would have our funeral.

  • This is Linda.

  • Linda is one of seven masks whose job was to stand there for 30 minutes

  • with her little hors d'oeuvre plate of dead crow

  • while I documented what happened.

  • Most importantly, though,

  • her job was to come back after a week,

  • now without the dead crow,

  • so that we could see if the birds would treat her just like any old pedestrian,

  • or if, instead, they would exhibit behaviors like alarm calling

  • or dive bombing

  • that would indicate that they perceived her as a predator.

  • Now, given that we already knew crows were capable of learning

  • and recognizing human faces,

  • it may come as no surprise that the majority of crows in our study

  • did treat the masks that they saw handling dead crows as threats

  • when they saw them over the course of the next six weeks.

  • Now, if you're sitting there thinking,

  • alright, give me a break,

  • look at that face, it is terrifying,

  • anyone would treat that as a threat

  • if they saw it walking down the street,

  • know that you are not alone.

  • As it turns out, a lot of the folks

  • whose houses we did these experiments in front of

  • felt the same way,

  • but we'll save that for another time.

  • So you may be comforted to know that we did control tests

  • to make sure that crows don't share our preconceived bias against masks

  • that look a bit like the female version of Hannibal Lecter.

  • Now, in addition to finding that crows were able to make associations with people

  • based on their handling of dead crows,

  • we also found that in the days following these funeral events,

  • as we continued to feed them,

  • that their willingness to come down to the food pile significantly diminished,

  • and we didn't see that same kind of decline in our control groups.

  • So that suggests that, yes, crows can make associations

  • with particular places where they've seen dead crows.

  • So together, what that tells us is that

  • while we certainly shouldn't discount those other explanations,

  • we can feel pretty confident in saying

  • that for crows, attention to their dead

  • might be a really important way

  • that these animals learn about danger.

  • And that's a nice, tidy little narrative

  • on which to hang our hats.

  • But in life and death,

  • things are rarely so neat,

  • and I really came face to face with that in a follow-up experiment,

  • where we were looking at how crows respond to dead crows

  • in the absence of any kind of predator.

  • And suffice it to say, we found that in these cases,

  • the wakes can get a little more weird.

  • So this is what that experimental setup looks like.

  • You can see our stuffed dead crow alone on the sidewalk,

  • and it's been placed on the territory of a pair.

  • (Squawk)

  • That is the alarm call by one of those territorial birds,

  • and it's coming into frame.

  • Pretty soon, its mate is going to join it.

  • And so far, this is all very usual.

  • This is what crows do.

  • OK, right now it's getting a little less usual.

  • Not everyone here might be familiar with what bird sex looks like,

  • so if you are not, this is what it looks like.

  • You're basically seeing a confluence of three behaviors:

  • alarm, as indicated by the alarm calling;

  • aggression, as indicated by the very forceful pecking

  • by both one of the copulatory birds and one of the excited bystanders;

  • and sexual arousal.

  • Clearly, this is startling,

  • and interesting to think about and talk about.

  • But if our goal is to understand

  • the big picture of how animals interact with their dead,

  • then the most important question we should ask is, is this representative?

  • Is this something that's happening consistently?

  • And that's why being able to do systematic studies with crows

  • is so valuable,

  • because after conducting hundreds of these trials,

  • where I was placing these dead crows out on the sidewalks

  • on the territories of hundreds of different pairs,

  • what we found was that, no, it's not.

  • Contact of any kind,

  • whether it was sexual, aggressive

  • or even just exploratory,

  • only occurred 30 percent of the time.

  • So given that this wasn't representative,

  • this was the minority,

  • we may be tempted to just dismiss it

  • as irrelevant, odd, creepy, weird crow behavior.

  • But what may surprise you is that behaviors like aggression

  • or even sexual arousal

  • aren't all that rare,

  • and certainly aren't constrained to just crows.

  • Because while the popular narrative when it comes to animal death behaviors

  • tends to focus on affiliative behaviors

  • like grooming or guarding,

  • that is far from the complete list of what even our closest relatives do

  • around their dead.

  • In fact, we've documented behaviors like biting, beating and even sex itself

  • in a wide variety of animals,

  • including many primates and dolphins.

  • So where does this leave us in our understanding of animals

  • and their death rituals?

  • Well, for crows, it suggests that,

  • like insects, they may have a strong adaptive driver

  • in their interest in their dead.

  • In this case, it might be danger learning,

  • and that might have acted as the inspiration

  • for our own rituals as well.

  • But when we look more closely,

  • we see that there's no one simple narrative

  • that can explain the vast array of behaviors

  • we see in crows and many other animals.

  • And that suggests that we are still far from completing that time machine.

  • But it's going to be a really fascinating ride.

  • Thank you.

  • (Applause)

Whether we want to or not, humans spend a great deal of time

Subtitles and vocabulary

Click the word to look it up Click the word to find further inforamtion about it