Do Animals Understand Death? The Latest Science Might Surprise You

Few things have earned as much as thought and attention in the collective human mind as death. For as long as we’ve had the capacity to express ourselves through words and other forms of communication, the subject of death and dying has loomed ever present. But Susana Monsó, a Spain-based philosopher, argues that while humanity’s particular flavor of fascination and dread at the notion of death may be unique, our perception of it actually isn’t.

Her book, Playing Possum: How Animals Understand Death, was first published in Spanish in 2021 but has now received an update and a revised English translation that will be out later next month. In the book, Monsó discusses the emerging field of science that seeks to understand how animals view and react to death. And she makes the strong case that humans are far from the only animals to know the meaning of dying, even if our vocabularies differ. Gizmodo spoke to Monsó about the origins of her book, the “romantics and killjoys” of animal cognition research, and why the possum’s ability to play dead reveals so much about how other animals grasp the nature of mortality. The following conversation has been edited and condensed for clarity.

Gizmodo: In your career as a philosopher, you’ve largely focused on discussing and better understanding the minds of nonhuman animals. But what specifically made you want to write a popular science book about how other animals experience the concept of death?

Monsó’: So academically speaking, I started working on this at a time where I was doing a postdoc and I needed a new topic that was completely different from my doctoral dissertation to apply for a project. And I thought of this topic because there had been a series of reports documenting animals’ reactions to the dead and the dying. I’m always sort of monitoring the latest research in comparative cognition, and this had really caught my eye as a new emerging field that was in need of some philosophical analysis of key concepts, some clarification of the core ideas at stake here. And it’s tied into my general interest, which has always been in those capacities that we think of as uniquely human, and that we tend to use to ground this idea of human exceptionalism—this sense of moral superiority that then allows us to exploit the natural world without really thinking about other beings.

But at the same time, I was about to turn 30, and I think it happens to a lot of people that when they approach that age they start to think a lot about death. I’ve heard this from several other people, and I think it has to do with with something about going into official adulthood, so to speak. So I became kind of obsessed with death in that time in my life. And at the time, I really didn’t link the two things in my head. I thought that my research was completely separated from this, but with time and distance, I realized that I also may have unconsciously turned to this topic because I needed answers myself. I needed to find a way of coping with my own existential fears.

Gizmodo: You point out that scientists and philosophers have only recently started to seriously study how animals respond to death, a field known as comparative thanatology. Why has it taken people, and particularly experts in cognition, so long to see animals as capable of understanding it?

Monsó: Comparative cognition in general is really wary of the dangers of anthropomorphism and anthropomorphizing animals.  Many years ago, before the cognitive revolution, psychologists weren’t even talking about the mental states of animals. They were just describing their behavior. And even though behaviorism is supposed to be a thing of the past, I think it still has some presence today, or at least some of its underlying assumptions are present in fields like contemporary comparative cognition. And I think that has a lot to do with the tendency of a lot of people to want to stay away from topics that sound very human-like, toward topics that could lead us to engage in anthropomorphism. That’s my guess. And this means there are several topics that it’s taken a while for scientists to take seriously, even nowadays.

Daniel Dennett [a well-respected philosopher and cognitive scientist who passed at the age of 82 this April] made this distinction between the romantics and the killjoys. And you can still see some scientists who are willing to talk in human terms about animals, are willing to talk about things like friendship and morality using these kinds of words, whereas others still want to use words that set us apart from animals, words like affiliation instead of friendship, or prosocial behavior instead of morality. And I understand why they are doing it, and I think the reasons are important. But I also think that there’s nothing wrong with asking certain questions, such as: Do animals understand death? So long as we study them very carefully and in a way that’s that’s very mindful of the fact that we could engage in anthropomorphism.

Gizmodo: Something that I really found interesting, not just in your book, but in reading the interviews and the reactions others have had so far, is that people will often talk about your book or about how animals see death through the lens of grief or mourning, framing it in the ways people tend to react to death. But you try to expand our understanding of death beyond that. Why is it important to perhaps disconnect ourselves from that human perspective?

Monsó: We do need to strike a balance between daring to ask these questions, but also being mindful of the fact that we are talking about other species with other ecologies, other social structures, other sensory capacities. They have different bodies and different ways of interacting with the world, of interacting with each other, of doing all sorts of things that they have to do for survival. So even if they have an understanding of death, they’re not going to have the same understanding that we do necessarily. And if they react emotionally to death, it’s not going to be necessarily like our own reactions.

And I think the topic of grief, it’s so entangled with the notion of understanding death that so many people have a lot of difficulties separating these two ideas—the idea of understanding death and the idea of grieving. But they are very different ideas. You can understand that someone has died without grieving that person. And in fact, we do that all the time. We hear about famous people dying, and we don’t grieve their deaths, because we don’t have a bond with them. And for animals in the wild, they have a lot of experience with death, and a lot of the deaths that they are going to witness are not going to be deaths of individuals that they care about, so it’s very unlikely that they’re going to grieve them. But this doesn’t mean that they don’t understand what’s going on.

Another thing is that death is very often a gain for a lot of animals. For predators, for instance, death is not a loss. it’s a gain. It means that they’re going to have a full stomach that night. So, I think it’s very important to separate these two ideas.

Gizmodo: You talk about lots of animals throughout the book, but it’s not until the end that you actually discuss the critter in your title, the humble possum [In North America, “possum” is colloquially used to refer to the Virginia opossum (Didelphis virginiana), though a related but distinct group of marsupials found in Australia are also often called possums as well]. Why are these marsupials in particular an important illustration of how death might be widely seen throughout the animal kingdom?

Monsó: Basically, in my book, I’m trying to argue that the concept of death is easier to acquire than we usually presuppose, and then we can expect it to be fairly widespread in nature. And the opossum provides one of the best pieces of evidence that we have of this, and that’s because she engages in a very elaborate death display whenever she feels threatened. She goes into what’s called thanatosis—this death feigning where she incorporates all sorts of signals of death. She adopts the bodily and facial expression of a corpse. Her body temperature drops. Her breathing and heart rate are reduced. She secretes this putrid smelling liquid, and she stops responding to the world. And if you didn’t know in advance about her little trick, you would be fooled by it for sure. Now, the opossum doesn’t necessarily understand what she’s doing. For her, this reaction is probably analogous to when we are in a state of fear and our pupils dilate, or our hair stands on end, and we’re not controlling this. We’re not even aware of this, but it happens automatically. For the opossum, it’s probably something like that. It’s probably also an automatic process. However, we need to have a reason why this defense mechanism evolved and why it has the shape that it has.

So a good way of thinking about this is by thinking, for instance, of the example of peacocks and their tail. Biologists often say that by looking at the peacock’s tail, we can get a glimpse of what the peahen finds sexy, right? Because the peacock’s tail is obviously a huge disadvantage in a lot of areas, but it’s very advantageous, because the peahen finds it sexy, so it makes it more likely for the peacock to reproduce. So by looking at the peacock’s tail, we can have a window into the mind of the peahen.

The opossum’s death display is similar in that it provides a window into the minds of her predators. There are several reasons why a predator might not want to eat an animal that’s already dead, or might prefer to store it for later consumption, and this can give the opossum a chance to escape. But for this to work, she needs to put on a convincing death display. So the opossum is a good piece of evidence that there are predators in the world with a concept of death, whose cognition has acted as a selection pressure and has given shape to the opossum’s display over many generations—because the more elaborate the display, the more convincing it was, the less likely it would be that she would get eaten, and so the more likely it would be that she would reproduce.

And the opossum is not the only animal who does this. There are other animals with very elaborate death displays, but they’re quite separate from each other in the tree of life, which suggests that these selection pressures are quite widespread, that they exist among different predators and different habitats. And so this, too, points to the concept of death being actually pretty widespread in nature.

Gizmodo: Your book provides a lot of really fascinating lessons and reminders about death and how it’s seen in the world. But what do you hope readers most take away from reading it?

Monsó: So my hope is that the book will reach readers who are scientifically curious, but not particularly into animals. Because I’m hoping that my book will help generate some awe for the natural world in these people, and maybe a will to pay more attention to animals and to discover how fascinating they are in their diversity, and in the many ways in which they live in the world. The people who love animals and who read my book, they’re already on my side, so to speak. But it’s my hope to reach these other people and to inspire in them this sense of respect for the natural world that I think is an inevitable consequence of simply paying attention to it and seeing how wondrous and amazing it really is.