What are crows thinking when they see death?

Full disclosure: I am not actually going to be able to tell you the answer to this question.  But I am going to get you closer than we have ever been before.  At least by my standards.  So now the question is where to begin…

Let’s begin by acknowledging that death means something to crows in a way that it doesn’t seem to mean something to most other animals, at least as far as we’ve recognized. What I mean by this is that crows don’t ignore their dead, they don’t reflexively flee from their dead, and they don’t just go about carrying out undertaking behaviors without a second thought (or a first thought).  They really see their dead and they respond in a variety of ways.  In my previous research, I found that generally, they respond to unfamiliar dead crows by alarm calling, followed by recruitment of other crows to the area to form a raucous group called a mob.  Then they disperse after about 15-30min.

DSC_1088

I’ve found that they do other things as well, like touching the bodies, though this really only happens in the spring.  When they touch them they might gently nudge, peck or even copulate with the crows, though that latter one is exceedingly rare.

Other people have seen more curious things though. Upon listening to my garbled explanation of my studies, my dental hygienist removed her hand from my mouth and proceed to explain, with detectable urgency, that she knew about these funerals.  That when she was a little girl living on her family’s farm her father shot a crow.  Instead of leaving, the others brought sticks and dropped them on their dead flockmate. She’d never forgotten it.

What these stories tell me is that how crows respond to death is complex, and we are still far from fully understanding all their behaviors.  And one of the hardest parts of this is that we can’t ask crows what they are doing.  Why did you leave a stick that one time?  Why did you rip up the body that other time?  Why did you call for 30min minutes until your voice choked out, while your neighbors a quarter mile away looked later at the same body and then left in silence to return to the dumpster?

This barrier means that we stand a high chance of either under or over-interpreting their behaviors around death; for example, being unable to accept that we might experience the grief of death uniquely, or being unable to accept that we, in fact, do not.  This is the challenge in studying how another organism responds to death, and it’s one I grapple with constantly.

There might, however, be one secret weapon into deeper parts of how crows respond to their dead that we can reach without needing a Dr. Doolittle-esque translator:  their brains.  While all animals only have a certain number of ways they can outwardly express themselves, how the brain responds to stimuli can tell you a great deal more about what an animal might be thinking.  Which brings us to my newest paper.1

Now before I go on, I’m going to say up front that I suspect this current study might not sit well with some of my readers. Until now all of my studies have used wild crows and did not require the handling of birds or any kind of direct manipulation.  Spying on the brains of animals, however, is not so hands-off.  It almost always requires surgery. And it’s almost always lethal. I say almost, because sometimes we can actually learn quite a lot without opening up an animal.  Without slicing up its brain. Without keeping it captive forever.  This is one of those times.

Most people are familiar in some capacity with functional neuroimaging, especially fMRI. It’s a way to look at how the brain responds to different stimuli without needing surgery or euthanasia. fMRI works by tracking blood flow while an awake subject encounters a stimulus.  It’s how we have uncovered that psychopaths don’t experience empathy when picturing others in pain, or that some dogs value praise from their owners more than food.2,3 Using fMRI in a non-human animal requires a great deal of training, however because fMRIs are big weird noisy machines that would be objectively terrifying for the uninitiated. Which means that they would never work with a wild crow.  So instead, our team used a different kind of non-invasive imaging technique to spy on the minds of crows: FDG-PET.

Unlike fMRI which tracks real-time blood flow, FDG-PET tracks metabolic activity and most importantly it can do so retroactively.  The FDG in FDG-PET, stands for fluorodeoxyglucose, which is a modified glucose molecule with a radioactive tracer attached to it. It’s the same stuff we give humans when we’re going to PET image them for, say, a tumor.  The modified part is that unlike most glucose, this stuff doesn’t break down, it gets stuck wherever the body used it up.  The tracer on the other hand, does wash out. Still, for a brief window of time-about 20 minutes after injection-we can stimulate an awake animal in a variety of way, visually, acoustically, etc., and the brain will use up the glucose (FDG) in order to process that information. The animal can then be anesthetized and placed into a PET machine where, via a mechanism involving photons and gamma rays that was far too complex for me to bother retaining beyond my graduate exams, the machine can detect the tracer.  The imaging process takes about 20min, after which the bird wakes up, none the wiser for the invasion of privacy.

Crow scanner
An anesthetized crow in our specially fitted PET scanner at the UW Medical Center. The wingtips are bound during the scanning process to keep the feathers tidy and out of harm’s way. Photo by Andy Reynolds for Audubon.

After a lot of image processing and analysis, we can then infer how active a particular area of the brain was while experiencing one stimulus relative to a control.  So while there are some advantages to an fMRI approach, FDG-PET is the only mechanism that allows us to see how a crow’s brain was responding while it was awake and unconstrained 20min ago, instead of while it is strapped down in a big scary scanner.  At the conclusion of the study, each subject is banded and released.  Although our study used only a modest 7 subjects (which is a normal sample size in the imaging world) it brings me great pride to report that, not only did all of our subjects survive, but all left our care with better or equivalent body condition than they came in with.  Some of them have even been resighted successfully breeding in a subsequent season. Again, when it comes to spying on animal brains, this is the exception, not the rule.

Release
My former advisor and coauthor of the current study, John Marzluff, releasing one of the subjects at the conclusion of the study. Photo by Andy Reynolds for Audubon.

So now that some of the technical details are out of the way let’s get down to brass tacks and talk about what we actually learned from all this.  Our lab has previously used this method to understand what neural circuits process different faces, like familiar friendly or dangerous faces, as well as how crows perceive different kinds of threats.  But on the heels of my fieldwork looking at their responses to dead crows,  we wanted to know more about what was going on in their brains.  So we had a two stimulus paradigm: a visual one where we compared brain activity between when crows saw a dead, unfamiliar crow, and a dead, unfamiliar, song sparrow (the control), and an auditory one, where we played them recordings of wild, unfamiliar crows reacting to dead crows, and unfamiliar crows begging (the control).

To aid with our analysis we selected 5 particular brain areas a priori, which means before the study, to examine for brain activity.  These sites included the hippocampus and striatum, which are responsible for fear and spatial learning, the septum and amgydala, which aid with social behaviors, conspecific recognition and affect, and the NCL or nidopallium caudolaterale, which is responsible for executive decision making like our prefrontal cortex.

Among the visual paradigm, what we found was that between the threatening (dead crow) and control groups (dead song sparrow and responses from three birds in a previous study that saw only an empty room) there weren’t a ton of differences in relative brain activity.  Crows that saw a dead crow didn’t show more activity in the regions associated with affect, social behaviors or fear learning.  Instead, what we found is that, like when they see a familiar threat like a hawk, it’s their executive center that shows the most difference.4  At first this was a surprise, but given the number of ways they can respond to their dead, and possibly because they didn’t know this bird, it makes sense that they might be wondering exactly what they should do in that moment.  In case you are tempted to think that might be what’s going anytime they’re in this strange situation, know that a previous study using the same approach found very different neurological responses to when they see familiar threats, new threats, and friendly people.4  So there’s no reason to suspect that the protocol alone is what was responsible for NCL activity.

With respect to the auditory tests, we detected even fewer differences.  The most notable finding was that both kinds of calls, alarm and begging, stimulated NCL activity relative to the birds that saw only an empty room.  I can’t pretend to know exactly what this means.  But it does bode well for my idea that crow communication is quite complex and context dependent, therefore requiring a great deal of brain power to decipher and interpret.  But I speculate.

So, as I said, while this study in no way provided definitive answers to, “What are crows thinking when they see death?,” it’s gotten us as close as we have ever come and given us some good ideas for what might be going on.  But as with all science, the first study is the one warranting most skepticism.  I have no doubt we will continue to learn much more in future and I can’t wait to see where this study fits into the vast field of knowledge that awaits us.

If you would like to read this study in its entirety (which is full of extra details, analysis, and explanation) check out this link, which will remain active until April 15th, 2020.  After that, shoot me an email if you want the PDF, I am more than happy to pass it along.  If you would like to read the popular science article from the Audubon where many of these photos were sourced, but that came out before this study was released, follow this link.

Literature cited
1. Swift KN, MarzlufF JM, Tempteton CN, Shimizu T, and Cross DJ. (2020). Brain activity underlying American crow processing of encounters with dead conspecifics. Behavioural Brain Research 385: https://doi.org/10.1016/j.bbr.2020.11254

2. Decety J, Chen C, Harenski C, Kiehl K. (2013). An fMRI study of affective perspective taking in individuals with psychopathy: imagining another in pain does not evoke empathy. Frontiers in Human Neuroscience: https://doi.org/10.3389/fnhum.2013.00489


3. Cook PF, Prichard A, Spivak M, Berns G. (2016). Awake canine fMRI predicts dogs’ preference for praise vs. food. Social Cognitive and Affective Neuroscience 11: 1853-1862


4. Cross DJ, Marzluff JM, Palmquist I, Minoshima S, Shimizu T, Miyaoke R. (2013). Distinct neural circuits underlie assessment of a diversity of natural dangers by American crows, Proc R SocB 280: 1–8

18 Comments

Filed under Being a scientist, Cognition, Crow behavior, Death, Graduate Research, New Research, Science

18 responses to “What are crows thinking when they see death?

  1. This is so fascinating! Thank you for sharing your research. I look forward to diving in in between virtual classroom sessions with students this week! Very cool Kaeli and crew!

  2. Couple of questions: You described the gathering around the corpse as a mob, why not murder? The second question isn’t related to your article but stays within the context of your research: I came across an article that talked about a symbiotic relationship between wolves and ravens where ravens serve as lookouts while wolves hunt and in return the wolves leave them a share of the kill. Do you have any more information on this topic?

    • A murder is a colloquial term not a scientific one. And the the thing about wolves and ravens is just a myth. Ravens do follow wolves around to steal from their kills but they do not return the favor.

  3. Wow! What a trip that post is.

    Our local band of crows usually just seem interested in eating. I almost get jealous to hear about other crows.

  4. Susan T

    I’ve always been fascinated by crow behavior, as my dad had kept them as free-roaming pets when he was young. So I grew up with a series of them in the 50s and I saw firsthand how intelligent they are. (Apologies on behalf of my late father for interfering in the lives of wild critters.)

    Years ago during an outbreak of bird disease, Pierce County had issued warnings about handling dead crows, plus a plea to bring corpses to the health department.

    Sadly, two crows did die in my yard, but upon subsequent testing, cause was not determined.

    One crow died a slow death in a birdbath, and a second crow sat vigil, cooing softly at intervals. I did not observe the second crow touching the other, but I can’t say that it didn’t occur.

    This all happened during a heatwave, and the second crow (visibly distressed-looking) never left until the first had been dead for awhile. I’m not sure if it sat vigil during the night, but it was there each morning in the same place.

    I love watching birds, and corvids are favorites. A few have befriended me and will “talk” to me, making a variety of vocalizations while I’m gardening or cleaning the birdbaths. One came last year that repeatedly said what sounded like “Bobby” and would respond if repeated back.

    Thank you for your enlightening research!

    -Sue

    💕

    >

  5. You don’t need an MRI to tell you what common sense knows. The crows feel the same as all mammals do about death. Sometimes it’s painful and sometimes they expect it, sometimes they feel sadness or justice. Why is this so hard to believe? The MRI is dangerous and unnecessary. Birds have acute senses and it would be torture to put them through that.

    I’ve seen a Blue Jay mourn the loss of its mate a few times. One died by drowning and its mate wouldn’t leave the site for days. Another one followed my cat around for 2 years squawking at it because he killed its mate. One day the bird just left the neighborhood and no birds follow him around like that one did. The crows sometimes squawk at him from a tree but they don’t go out of their way to follow him. Some other birds, I think they were finches, the parents flew around my cat after he tried to get the baby when it was learning how to fly. They swooped over and over his head until i brought him inside and then they darted aggressively outside my window. He didn’t even kill that bird but tried to yet they kept trying to fly by our window as if they were gonna attack. Some animals are very brave.

    • I just want to be clear that you-the person with the cat who has killed at least one bird and clearly would like to kill another-is complaining to me about a lack compassion for the birds in our study that were all eventually released with a good bill of health? Do I have that right?

      • I don’t look to my cat or other animals for moral guidance. You have a right to follow your conscience and I have a right to follow mine. It is unnecessary to put crows through MRIs or subject animals to lab experiments when we should let common sense dictate observation. If you really need to prove that animals have emotions then I suggest you give your colleagues brain scans and try to figure that out instead of wasting time and money trying to prove obvious observations. I’m so tired of “reason” being an excuse for illogical skepticism. Haven’t we evolved past dogmatic “science”? What part of the brain does arrogant stupidity stem from and what makes it so influential to other human animals who delude themselves into thinking they are so superior that they’re the only mammal on earth that can feel sorrow, wonder, or pain.

      • You keep calling it an MRI and harping on this idea I reject the notion that animals feel things. Both are addresses in the article which makes me think you didn’t bother to read it.

        Again though, no birds were killed to make my point. Seems clear you can’t say the same. If your cat is killing birds that’s on you, not your cat. You’re expected to be the adult and prevent wanton killing, not your pet.

      • When I was about five years old I saw hundreds of birds gather in my backyard and squawk at my other cat who used to kill mice and birds on a daily basis. This cat was the alpha of the neighborhood and ruled a huge cat colony. One day the birds all ganged together and chirped like banshees at him as he sat there looking up at them the way a well fed, tired, and content cat often gazes at things it has no further interest in. My histrionic mother and ten year old sister were crying and very frightened so they yelled at me like it was my fault for keeping the cat who was mostly feral btw. My mom threatened to call the anti cruelty society of Chicago so I naturally had to overcome my fears and step outside to shoo the birds away or else his entire colony would get exposed. Back then in 1980 they didn’t spay or neuter cats but rather euthanized them after rounding them up. By that time I saw several cat colonies collapse and I didn’t want them to take them away despite the fact that they ate birds and mice. Friskey, my cat, preferred wild food over store bought kibble. I only fed him in the winter. He’d come home only after a fight or when food was scarce. The point is that we all see animals do things that show they have emotions but only recently have “scientists” acknowledged phenomena that signifies animal’s emotional intelligence. For most of our history doctors and scientists were trained to believe that animals don’t have feelings. The fact that you had to “prove” this through lab experiments is actually quite comical.

    • Although reluctant to get involved in this discussion, I cannot see good science be so carelessly tossed aside without defending it.

      For starters, Newart, you speak of “common sense”. But what is commonly believed does not equate to it being true, and the very point of scientific study is to test these situations. To stay close to the relevant subject, people used to believe that crows and their relatives were responsible for spreading death: after all, were they not always on site when a cow had died, or a sheep gave birth to a dead lamb? Naturally, these birds are simply very observant scavengers who knew perfectly where to find a good meal, but the farmers mistook effect for cause. Where I used to live, ravens were completely exterminated because of this belief. They only returned after this stupidity was refuted, and some biologists spent decades reintroducing them. Sometimes, “common sense” can of course be entirely correct (the use of willow bark as medicine being a famous example of something that worked, even if nobody knew why). Sometimes, it’s completely wrong, based on faulty connections of cause and effect, or nothing but superstitions (the medieval belief that smell spread diseases for example, so keeping some perfume near your nose would keep you safe from the plague). How would you suggest separating the wheat from the chaff? Perhaps ensure that rather than anecdotal evidence, there are repeated observations of certain correlating events? Perhaps manipulate the situation, so that it is clear which of the observations causes the other? Perhaps aim to understand the observations by delving into the underlying mechanics? Well, that’s science. Science is not one peculiar, particular way in which some elites in their ivory towers look at things everybody else already knows. It is meticulously ensuring that what we think to know is actually true, because in the end, that is the only foundation you can build on.

      I find it interesting that you seem to think that you are in the opposite camp from the author here. The methods outlined in the piece above clearly demonstrate a great care for her research species. The fact that this method is relatively non-invasive and potentially completely harmless is repeated several times, and clearly celebrated. From experience, I can tell you that this is not exactly common in biological research. But before you blame those stupid scientists for this, this is purely a reflection of society. If birds and non-human mammals were acknowledged to have the emotional capacity that they likely have, do you think they would be raised and slaughtered in the way that they are? Only in recent years, when the idea that other animals may in fact be not so different from us has started to gain traction, you see that more and more people choose to alter their lifestyles to deal with this fact — be it to improve the welfare of pets, livestock or research subjects. Where do you reckon this idea stems from? Certainly not traditional beliefs, because those, by definition, do not tend to change. Or could it possibly have something to do with biologists who observe, describe and test the real ability of other animals to reason, to feel, and indeed to mourn? People like the author here are the ones who are creating and spreading this knowledge. You are not so much barking up the wrong tree, as ranting blindly against an imagined one.

      • Without having an ability to rely on natural observation makes the scientist incapable of understanding results from any experiment. You can’t simulate natural emotions in an artificial environment let alone repeat them. At some point we have to use common sense.

        Common sense is a virtue, not an inferior cognitive function as you were trained to believe. When any animal displays emotion in a natural setting, you can’t verify that by trying to reproduce it in a simulated one or lab. Have you ever fallen in love? What is that? Have you ever experienced pain from losing a loved one? Could you reproduce those results repeatedly in a lab? What part if the brain does it stem from? Do you realize that our brain chemicals change each moment?

        In the time it takes you to inhale your next breath I have experienced all the emotions you will never understand.

      • Since you asked…yes actually we have used functional neuroimaging to better understand love and pain in the human brain. Here’s a review in fact entitled “Neuroimaging of Love”. https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1743-6109.2010.01999.x?casa_token=9aZQKn5VVNMAAAAA:wx_HPo7m_beRucW6fFrXIacUGgAacouAh873pDLEt–ucvs48mz0LrDlXCsJSECbSaebpH87clwo72U

        We have also used brain imaging to see how the brain responds when people experience grief. We cited some of these paper in ours, (which I still encourage you to actually read-and can be found at the bottom of the blog article). Here’s one entitled “the functional neuroanatomy of grief” https://ajp.psychiatryonline.org/doi/full/10.1176/appi.ajp.160.11.1946

        Love and grief are controlled by the limbic system, which is a composed of multiple parts of the brain but the primary part involved in these experiences is the amygdala. If you are interested, we could even dive into the neurotransmitters (or brain chemicals as you all them) that facilitate these systems, because yes we can and have measured them. In fact that’s a really interesting case study of an old Parkinson’s drug causing gambling addictions specifically because it tapped into these systems in ways they hadn’t previously understood. I think there’s a Radiolab episode about that…

        Why is it important that we understand this in humans? Because it an tell us a lot about when and why people are sometimes incapable of expressing emotions, or how we might treat people whose processing of them are hurting themselves or others. So while you scoff at the idea we could ever look to the brain to tell us anything about emotion, know that we have and are already doing that in humans and it has lead to crucial improvements in treating emotional disorders like PTSD. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3142267/

        I don’t disagree at all though that this study is by no means a conclusive look at the crow brain during these experiences, and I’m not sure how I could have made that more clear to you in the article. We should be skeptical of these results and I agree that in cases where a crow’s mate dies they are probably responding differently then we have been able to show. The jay’s whose mate was killed by your cat may well have been quite sad. So let’s prevent that from happening again, ok? Please keep your cats inside.

      • If you really believe that love and grief are controlled by the limbic system then you have proven to me through my common sense and natural observation that you are arrogant. Arrogance creates a bias. Biased mindsets make for faulty research.

        Your ego is too big for me to get through to you. Why did you get so triggered by me? I find your arrogance fascinating. Where is the ego? Can you point to that on an MRI? You can’t blame your limbic system for all your emotional reactions. At some point we make a conscious choice to connect or disconnect emotionally and/or cognitively.

        Read my posts again and analyze your responses. Do you have self-awareness? That is a requirement for observation. An observer is only reliable if he or she is self-aware of possible biases.

        My hypothesis: I think it’s possible that you know this is all unnecessary. I think you were triggered because deep down you know that you get paid to spout scientific mystique. You keep going on about my cats being killers and blaming me for being an irresponsible pet owner but refuse to acknowledge my story about the bird gang.

        I don’t care if my hypothesis is correct. I’m willing to put aside my ego. That’s the difference between common sense observation and one that sets out to prove something. You want to prove me wrong at the expense of seeing any truth I might reveal. Humans go to great lengths to prove what they want to believe. I wish it didn’t have to be that way. We create unnecessary drama when we don’t have faith in our perception.

        Have you ever considered that your perceptions were abused and that’s why you feel a need to create scientific data? Perhaps your emotional response stems from trauma by a hierarchy and that’s why you try so hard to prove the obvious.

      • It’s pretty simple: I was triggered because you’re letting your cats kills birds. Cats kill billions of birds a year in the US alone. It’s a big deal. We should do something about it.

        And yes, it’s no mystery that getting killed is something they really don’t like, which is why they mobbed (or as you put it “ganged’) up on your cat. That’s absolutely something birds do. What you describe makes perfect sense to me and I’ve both witnessed and reproduced that behavior (check out some of the studies I linked to in the article). I didn’t address it because there was no reason to question that some birds mob cats. That’s what they do. Crows mob predators like cats and eagles. Red-winged blackbirds mob crows.

        I don’t really care what your opinion of the study at large is. Go ahead and think it’s all nonsense, I have no interest in debating that. But if you ask a science question like, what part of the brain is responsible for love, I’ll answer, that’s my job. Oh which, BTW, here’s a paper that discusses the neural basis of arrogance. https://www.sciencedirect.com/science/article/abs/pii/S0028393209002577

        Again, just keep your cats inside. That’s literally the only thing I have any interest in debating with you. Hey they’ll be good company since we’re all self isolating anyway, right?

  6. I don’t really care that you missed the findings of the study, just please keep your cat inside and stop letting them kill birds.

  7. I must say your findings are amazing. We do not really have the time do such things as you have done. Thanks for the enlightenment.

  8. Pingback: Rook Gibbets & Crow Funerals | Birding Walks in RXland

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