Susana Monsó: There’s surprisingly little literature on the question of whether animals can understand death.

Paul Rand: That’s Susana Monsó, an associate professor in the Department of Logic, history and philosophy at UNED Madrid and the author of a new book, Playing Possum: How Animals Understand Death.

Susana Monsó: If you look at what philosophers tend to say, they tend to agree on this specific idea that animals cannot understand death.

Paul Rand: Does your dog understand that they will die one day? Does a lion hunting a zebra know that it is murdering or is it just trying to get food?

Susana Monsó: They tend to think of it as something obvious, that only humans can understand death. And this is already something very surprising because if there’s something that characterizes philosophers is our tendency to disagree with each other. We love to debate every single thing. So for me, whenever I find something on which all philosophers agree, it’s a sign for me that there’s something fishy going on.

If my research has taught me anything, it’s that there is a lot in common between humans and other animals, and it’s very difficult to find capacity that sets us apart.

Paul Rand: Death is all around us and we’ve become so used to it that we forget to stop and think about how complicated a concept it is to truly grasp.

Susana Monsó: So this idea that understanding death requires very sophisticated psychological capacities. That the concept of death is it’s an abstract concept that requires us to understand infinity and the concept of absence and the concept of time and so on, all these very demanding capacities.

Paul Rand: But Monso’s research took her on a philosophical journey into the vast minds of the animal kingdom, and what she discovered is more surprising than you might think.

Susana Monsó: I wanted to help people think about the amazing minds of animals and how there’s so much that we don’t know and how they can surprise us in so many ways. And my hope is to put my little grain of salt in contributing towards a greater respect for the animal world, in general.

Paul Rand: If animals can understand death, well, what does that say about whether they have a morality or should have a morality? And what should that mean for our relationship to them?

Susana Monsó: Many philosophers have theorized about animals and happiness and what makes for a good life. And a lot of them have talked about whether death harms animals? Whether it’s okay to kill an animal? It’s morally okay?

Paul Rand: From the University of Chicago Podcast Network, welcome to Big Brains, the show where we explore the groundbreaking research and discoveries that are transforming our world. I’m your host, Paul Rand. Join me as we meet the minds behind the breakthroughs. On today’s episode, do animals understand the concept of death?

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Susana Monsó: So there’s an academic answer to that question and then more of a personal one. Academically speaking, I was doing a post-doc at the time and I needed a new topic on which to focus my research on that was different from my PhD. And my PhD had been on animal morality. The question of whether animals can behave morally, for instance, whether they can have empathy? I’ve always been interested in capacities that we tend to think of as uniquely human, but also personally speaking, I was about to turn 30 at the time and as often happens when you change decade, I had become obsessed with death and-

Paul Rand: Not usually that young, but...

Susana Monsó: Not usually that young. I’ve always been a bit of a goth, but I’ve heard it happened to other people, so, it’s also not that rare. But yeah, so I became obsessed with it at a very personal level.

Paul Rand: All right. Well, you also talk about an episode as a child of all things with an ant?

Susana Monsó: Sure. So I must have been about eight or so, I guess I was a bit of a nerd already, that young and I had been given a microscope. Once you have a toy microscope, it’s not that easy to find interesting stuff to actually look at, right? So at some point, I came up with the idea of looking at an ant and I wanted her to be intact. I wanted to be able to look at the intact body of the ant. So I came up with the idea of getting an ant from our garden and putting her inside a little sample tube that came with my microscope until the ant ran out of oxygen and then she would die and she would look intact. It takes a surprisingly long amount of time for an ant to die inside a little sample tube. So after several hours, the ant still hadn’t died. And then I had this moment where I completely, spontaneously, without the intervention of any adult just came to realize that what I was doing was actually very cruel.

And all of a sudden, it seemed like completely unacceptable for me to take this innocent being’s life. And I remember the moment of the unbearable sadness of what I was doing to her, being just too much and deciding I had to free her. And I remember distinctly the moment of going up to this little rose bush that was in the garden and opening the sample tube and letting her out and feeling like it was the right thing to do. And it’s very interesting because no adult had told me to do that. No one was there looking at me. It was just like me and the ant and a moment of empathy between the two of us.

Paul Rand: The question is, would that ant have understood that it was dying? Would it even understand what death is at all? It turns out that ants, like the one Monso had in childhood are actually the perfect animal to illustrate why we can’t just assume animals understand what death is.

Susana Monsó: So ants and other eusocial insects have what we call stereotyped or stereotypical reactions to death. The animals are born with these tendencies to carry out these behaviors which have to do with corpse management. And one of these, for instance, is what’s called necrophoresis, which consists of picking up a corpse and taking it out of the nest and into the refuse pile, which is outside of the colony. This presupposes that the ants can tell apart live individuals from dead ones, right? But we know that they don’t actually understand death because this behavior of theirs is dependent on the presence of certain cues of death, such as certain pheromones that are given off by corpses. And when they detect these pheromones, they pick up the corpse and they take it out into the refuse pile.

And we know it’s these chemicals that cause these reactions because if you take some of these chemicals and you put them on a little piece of leaf or a pebble, the others are going to treat it as though it were a corpse. They’re going to just pick them up and take them out into the refuse pile. So we know that they’re not really understanding what’s going on, they’re just offering this pre-programmed response to certain stimuli.

Paul Rand: Scientists can even add these pheromones to a living ant and they will carry them out of the nest.

Susana Monsó: If an animal actually understands death, it’s much more difficult to trick them.

Paul Rand: But wait, anyone who’s watched a planet earth documentary might be saying, “Don’t we have proof that animals understand death because we’ve seen them grieving?”

Susana Monsó: So grief is like the paradigmatic emotion that we associate with death. And a lot of the empirical study of animals’ relationship with death has been looking for signs of grief in animals. And indeed, there’s a lot of evidence that animals can grieve. One of the most convincing pieces of evidence is this phenomenon that’s called deceased infant carrying. So it’s a phenomenon of mothers who cling on to their corpses of their babies. And this is something that we see in a lot of mammalian mothers. For instance, maybe listeners have heard of the story of Tahlequah, this orca who became famous in 2018 because she carried her baby for 17 days and over 1000 miles.

Tape: Now the mother whale in the northwest and her apparent act of mourning. It’s a scene that has researchers taking a close look at the emotions of these massive creatures.

Susana Monsó: As far as I know, she is carrying another of her babies who has also died, and I’m not sure if she’s still carrying it, but she’s certainly... What has been in the newspapers recently, because they’ve seen her again doing the same thing.

Tape: In late December, the Center for Whale Research reported J35, also known as Tahlequah, had given birth to a calf J61. But by the New Year, it was confirmed the baby did not survive, and now, history is repeating itself.

Susana Monsó: So it’s really heartbreaking and it seems to be an indication that she’s grieving this loss, that she’s not fully accepting the death of her baby.

Paul Rand: But we’re not in Tahlequah’s mind. How can we really know that she understands that her baby is dead? Perhaps she was carrying the body because she thought it was still alive and didn’t want to leave it behind. But even if she was grieving, does that mean she knows the baby is what we understand, to be dead?

Susana Monsó: I spend a lot of time in the book arguing that these are two distinct questions and that we need to treat them as such. On the one hand, this is because you can have grief without understanding death. We speak of grief when someone that we love moves to a different country or when a relationship that lasted a long time ends. And these are moments where there’s no death, but there’s a grieving process and we see an animal sometimes, reactions of grief that might not imply that the animal is understanding death, they’re just missing the person or the individual that they love and who is not there. And that’s what grief is signaling.

Grief is telling us that there is an emotional bond that’s very strong and that has been broken for some reason. And understanding death is different. You can understand death without grieving. And we do this all the time. Whenever we’re reading the newspaper and we come across the news that some famous person has died, we can process this, we can integrate it, we can understand it without grieving. The key idea is that they’re two separate phenomena. So, if we want to understand how animals understand death, we need to look beyond grief because if we’re only focused on grief, we’re going to be missing many, many pieces of the puzzle.

Paul Rand: Another way to wrap our heads around why we shouldn’t assume that animals understand death is by looking at another animal that we’re much more familiar with, humans.

Susana Monsó: Human children don’t learn about death overnight, but it takes them about 10 years to fully master a scientific concept of death. Some aspects of death are hard for children to grasp, like the irreversibility of it, for instance. When grandma dies and suddenly she’s not there, they have to grasp that she’s never going to be there again, which is really hard for them. But it doesn’t stop in childhood. Throughout life, you learn more things about death. You learn what sort of things can cause death. You don’t learn all of them when you’re 10, but rather, as you go through life, you acquire more and more knowledge about this. And there are cultural variations, there are variations across time. So think about our relation to death versus the relation of ancient Egyptians to death. It’s very, very different. And there are also individual variations. I might have a different conception of death to my Catholic grandmothers and we may have different ways of relating to it.

I had my existential crisis at 30, other people may have it at 50. The concept of death is always a spectrum, so it’s not an all or nothing matter, but rather, you can understand death to different degrees of complexity. And Miguel de Unamuno, he’s a Spanish philosopher from the 20th century, has a beautiful book where he’s talking about his experience with the phenomenon of mortality. And one of the things that he says in this beautiful little book is, “It’s so hard to integrate emotionally the fact that we’re going to die because our brains are not equipped with the capacity to grasp the non-existence of our own consciousness.” Try to imagine this. Try to imagine your own mind not existing and how that’s... It’s impossible. It just causes this dizziness and you can’t do it, right? And so, I use this quote to illustrate the fact that if we were to talk in strict all or nothing terms, humans wouldn’t understand death either because there are these limitations in our own intellect that prevent us from fully grasping what it means to die.

We can’t assume that the concept of death is an all or nothing matter, which is usually how it’s been viewed. And so, it’s been understood in this very binary way. And so we’re like, well, animals don’t have the all, so they have nothing at all. And that’s not the right way of viewing the question. You need to understand it as a spectrum. And so, you need to ask how complex can animals understanding of death come to be? And that’s going to depend on their experiences. There might be some limits to how much they can actually understand about death.

For instance, I think that the inevitability of death is quite hard, if not impossible to understand without some kind of linguistic scaffolding because the only reason that you know about the inevitability of death, it’s because humans, generation after generation, have told each other that everyone dies eventually. And so, we know that we’re going to die inevitably because we’ve been told. And if you weren’t told, it would be very difficult for you to reach that conclusion on your own because you don’t have enough of an inductive base to reach that conclusion in your own lifetime.

Paul Rand: So, if the understanding of death is on a spectrum, the question is, where do certain animals fall on that spectrum? That is after the break.

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Understanding the concept of death is a spectrum, but for animals to fall on that scale at all, they must at least reach the threshold at the furthest end. Monso calls this the minimal concept of death.

Susana Monsó: For me, you start to understand death once you can understand two key ideas, which are the notions of non-functionality and irreversibility, the idea that dead individuals don’t do things, that this is an irreversible state.

Paul Rand: Just like human children, animals must go through experiences that develop this minimal concept of death. Monso argues this happens in three crucial ways. What she calls the holy trinity.

Susana Monsó: And the holy trinity is made up of three things, cognition, emotion, and experience. You need the three things in order to reach some understanding of death.

Paul Rand: To see how this process happens in the wild, one of the best animals to focus on is elephants.

Susana Monsó: So, elephants are the typical animal that everyone thinks of whenever I mention that I study animals and death because we’ve all heard of these elephant graveyards and there are all these myths surrounding them. It seems that elephant graveyards are a myth, but they certainly do have all the ingredients in place to have a concept of death. First of all, they have very high levels of cognition. They’re very intelligent. They have excellent memories, and they have also a kind of intelligent that’s very attuned to the social sphere. So they pay attention to each other and they know a lot about each other. This is going to be something that’s going to be in place when one of them dies. They’re going to notice that this individual is not behaving as they normally would. It’s also easy for them to have the right kinds of emotions because these emotions are important because they’re what modulates our attention.

We need a certain emotion to be there for you to pay attention to a corpse. So you need to find the corpse interesting in some way because it’s exciting or scary or confusing. There has to be some emotion in place there. They also have very high levels of the emotion component because they are very bonded with each other, especially with the young elephants, with the babies. I was once at a conference where an elephant expert told me, “When there’s a baby born, and if the mother presents the baby to you, you better fawn over it for half an hour at least.”

Paul Rand: Oh gosh, okay.

Susana Monsó: “Otherwise the mother’s going to be angry.” You better show me that my baby’s beautiful.

Paul Rand: Okay, wow.

Susana Monsó: So, babies are very, very important for them. And also, the last factor is experience. Animals are not born with a concept of death, but rather, that they need to accumulate experiences with death in order to learn about it. And the experience factor is going to be high because they live very long lives, if they reach maturity. But again, there’s a very high infant mortality among elephants. When there’s a death in the group, elephants tend to be very interested in corpses. They have been seen visiting the remains of strange elephants. Elephants that they didn’t know. They don’t show this kind of interest in the corpses of other species. It’s only the corpses of conspecifics.

And there was, very recently, a fascinating report that documented that several baby elephant corpses have been found buried within tea plantations in India. And we don’t know who did this, it might’ve been humans, but there were some indications that it might’ve been elephants because there were elephant footprints and excrements around and people had heard elephant vocalizations in the area. And the five corpses which were found in geographically quite separate areas, were all buried in the same way with belly up and with their legs sticking out from the soil. So we don’t know what this means. It might just be humans doing this, but I wouldn’t be entirely surprised if it had been elephants because they’re also very cultural beings. And it could be that we are witnessing the birth of a tradition in these communities. So yeah, I wouldn’t bet any amount of money on this, but I also wouldn’t be surprised if it were elephants.

Paul Rand: Monso argues there are many animals that are likely to cross the threshold into a minimal concept of death through their experiences, but not all. In fact, it’s likely that our closest furry friends, dogs and cats probably have no concept of death at all.

Susana Monsó: I think that in general, domestic animals tend to be quite shielded from death. There are exceptions, of course. There are a lot of people who have cats go out into the backyard and they might hunt birds and so on.

Paul Rand: One way we may be able to see a lack of understanding of death in our furry companions is what often happens when owners die alone with their dogs.

Susana Monsó: Something that happens that, it’s something that I like to tell people about, but it tends to shock people a lot. And it’s that, in very high proportion of times when someone dies in the company of their dog, they end up being eaten. This is something that’s very common.

Paul Rand: Yeah, yeah.

Susana Monsó: A lot of people are shocked by this and they’re like... I can see the fear in people’s faces whenever I tell this story in front of an audience. Maybe thinking, oh my God, maybe my dog doesn’t love me. And I don’t think that’s the case. I think that we have a lot of scientific evidence that dogs actually love us. That’s pretty well established scientifically speaking. So what could be going on here?

So dogs, we tend to think of them as companion animals, but a lot of them live in the wild, they’re free-ranging or they live in the streets and they’re hunters, but they’re also scavengers. And when they feed on a corpse, what they tend to feed on is the torso where all the nutrient-rich organs are. But when a dog feeds on their human caregiver, what they eat is the face. And this is very interesting because our face is our communicative center. So this hints at the idea that what the dog is doing initially, is trying to get a reaction from the owner. And when they can’t, they get frustrated. And when a dog gets frustrated or stressed, the way they calm themselves down is with their mouths. They tend to lick things and nibble on things, and that’s how they de-stress themselves.

And so, they might start licking the face nibbling on it until they draw blood, and then one thing leads to another. But at the core, at the root of this behavior might precisely be their love for their caregiver, which is very interesting because it’s a manifestation of this love in a way that’s very different from how it would manifest in a human. For a lot of dogs in urban areas, their experience with death is going to be very, very low. And so, I think a lot of them are not going to have much knowledge about this, and this is going to mean that we might have to decide what we’re going to do, say if we live with two different dogs and one of them needs to be euthanized, we’re going to have to take into account the other dog and whether we want them to understand what is going to happen.

Paul Rand: If the minimal concept of death is on one end of the spectrum, what concepts of death are possibly further into the scale? One that Monso develops is called the natural concept of death.

Susana Monsó: And what I argue is that the natural concept of death is probably going to be a bit more developed than just the minimal concept of death. It’s usually going to have some presence of the understanding of the causal factors that are related to death and some presence of the component of universality. So the idea that death can happen to different individuals.

Paul Rand: The minimal concept of death only allows an animal to process what has happened to a single animal that has died. The natural concept of death, in contrast, also allows them to predict what could happen to others who were still alive if they encounter the same lethal causes as their dead mates.

Susana Monsó: And this is because there’s a high prevalence in nature of mechanisms of associative learning and inductive generalization that are going to allow animals to realize, animals who’ve seen several different individuals succumb to a predator like a leopard, to generalize beyond the here and now and say, “Oh, if these other individuals were to encounter a leopard, then they might also die.”

Paul Rand: This raises the question that you probably have been asking yourself. Can these animals also comprehend that they too will eventually die?

Susana Monsó: For an animal to understand her own mortality, she needs to somehow turn the focus onto her and think of herself also as a body that can break down irreparably at some point. I think it requires a level of self-awareness that might not be available to that many animals. So the cognition involved is more sophisticated, is what I mean. And also, I think that if animals reach an understanding of their personal mortality, it’s not going to have this character of inevitability as humans think of their personal mortality because of what I said before, how, you need this linguistic scaffolding to reach that understanding. So for animals who understand their own personal mortality, it’s more likely that they’re going to understand it as the idea that they can die, say if they encounter a leopard, but not that they will die.

Paul Rand: So no existential crises going on in the animal world?

Susana Monsó: I don’t think so. I think they’re spared that for the most part, yeah.

Paul Rand: From Monso, the prey and predator relationship is actually the perfect place to look for an understanding of death. But to get to that, first, we must turn to the possum.

Susana Monsó: So the opossum is on the cover of my book, not only because they are a very cool animal, very cute and very cool, but most importantly, because they are the last and I would say, most crucial piece of the puzzle that I build in the book, because of this behavior that she engages in, which is called Thanatosis. So Thanatosis consists of playing dead or playing possum.

And the possum, we have this idiom to play possum precisely because she’s extremely good at this. So when they play dead, they adopt the bodily and facial expression of a corpse. Their bodily functions are reduced, their breathing slows down, their heart rate slows down. They turn cold, their tongue hangs from their mouth and adopts this bluish hue. They expel this putrid smelling liquid from their glands, and they just stop responding to the world. So, if you didn’t know ahead of time of her little trick, you would be fooled by it for sure. This is a very interesting behavior, not because of what it tells us about the opossum’s mind.

For the opossum, this is probably just an automatic reaction to a threat, like when our pupils dilate or hair stands on end when we are fearful, it’s not something that they can control. But it’s very interesting because of what it tells us about the minds of her predators. The predators that she is aiming to deceive with this behavior. And I say aiming of course, in scare quotes because it’s not an intention in her mind. Why is this interesting?

Well, if the opossum’s behavior exists, we have to give an evolutionary story for how it evolved. And the thing is, that it’s a very complex behavior and it’s made up of all these heterogeneous components that have no real reason to hang together. The reason why they’re hanging together is because there’s an evolutionary pressure that has shaped the opossum’s behavior, given shape to it, and this pressure has been the concept of death of her deceived predators. So the more convincing the opossum’s display, the less likely she’s going to get eaten and by a predator because a predator is going to maybe discard her because they’re looking for fresh meat. Or maybe they’re cashing her for later consumption and she gets a chance to escape. But this is only going to work if she pulls off a very convincing display.

Paul Rand: If Thanatosis has evolved, it’s because there’s some advantages that comes from appearing specifically dead, not just to sleep or non-responsive, because then the predators would still consume them. The selection pressure that gave shape to these death displays is the predator’s concept of death.

Susana Monsó: So how the opossum plays death shows us how her predators understand death, what they find convincing display.

Paul Rand: And Thanatosis is quite widespread in the animal kingdom. We find all sorts of elaborate death displays in amphibians, reptiles, birds, and mammals. So the concept of death must also be quite widespread. This raises all sorts of questions about whether animals have morality and ethics? Whether their understanding of death should change how we think about killing and eating them? And this sort of philosophical thinking is exactly what Monso helps people take away from her book.

Susana Monsó: Well, the reactions have been interesting. A lot of people who pick up my book are not expecting an academic book. So the book, it’s adapted for a wide audience, but I think a lot of people are not expected to have to think through these issues with me, think through all the philosophical arguments. I think a lot of them are expecting just a book of animal anecdotes. And this is not a book of animal anecdotes. There are a lot of animal anecdotes in it, but it’s a philosophical book that is making a philosophical argument, and I think a lot of people weren’t prepared for that.

But what I wanted to do with this book was partly to vindicate philosophy as a discipline and the role that philosophy can play in the science of animal minds and how there is an important role to play. The science can only take you so far, but there’s a certain point where you have to interpret the scientific results, and you need philosophy in order to do that. It is important that the book is a philosophy book, and I had at least one person in my life, a friend of mine who’s a biologist. She read it and she was like, “I finally understood what philosophy is for,” and that was amazing. That was the best compliment it could give me, because that’s 100% what I intended.

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