From the Vault: The Remarkable Beaver, Part 1

Published May 25, 2024, 10:00 AM

Beavers are incredible creatures and significant ecosystem manipulators, but they’ve also been subject to various written and illustrative inaccuracies. Medieval bestiaries often depict the common beaver as a weird-looking dog that bites off its own testicles when pursued by mounted hunters. In this classic episode of Stuff to Blow Your Mind, Rob and Joe explore the meaning of these inaccuracies as well as the actual biological wonder of North American and Eurasian beavers. (part 1 of 2, originally published 05/18/2023)

Hey, welcome to Stuff to Blow Your Mind. My name is Robert.

Lamb and I am Joe McCormick. And it's Saturday, so we're going into the vault for an older episode of Stuff to Blow Your Mind. This one originally published May eighteenth, twenty twenty three, and it is part one of our series on the beaver, a truly remarkable animal, far more strange and amazing than you might imagine.

Yeah, so have you skipped it the first time around, thinking I don't want to hear about beavers. Beavers are boring. Well, you were wrong. Beavers are exciting and allow us to prove this to you in this episode and the following.

Welcome to Stuff to Blow your Mind, a production of iHeartRadio.

Hey, welcome to Stuff to Blow your Mind. My name is Robert Lamb and I'm Joe McCormick. We've covered numerous examples of this before, but obviously, in days before photography and videography, one had to depend on illustrations and written descriptions to convey the reality of an organism, you know, be it a bird or a fish, what have you. But this is especially true for creatures that lived in lands beyond your direct experience. You know, what are the what are the mammals, what are the birds? Like on another continent. Well, you have to send people out in the world. They can, you know, to a certain extent. They can bring specimens back. Certainly, they can bring parts of specimens back, but it's those ill in some cases, but it's those illustrations that really bring things alive. Now, certainly there are some fine examples of naturalist illustration out there, especially from recent centuries. I mean there's some gorgeous, like you say, like Audubond illustrations and paintings that sort of thing. But there are also countless examples, and we've touched on these before in the show of rough or drawings, drawings that feel like, you know, there's been a game of telephone at play. And this is especially the case for examples found in various bestiaries and medieval manuscripts, among other places. And when we think of such misconstrued animals, you know, what do we tend to think about? You know, we think about the rhino, We think about the lion, the whale, the elephant, you know, great animals, apex, predators, and megafauna. But in this episode, in the next episode, at the very least, we're going to get into another creature that has also experienced extreme inaccuracy in historic illustration, and that is the common beaver. Based on just some of the images we've been looking at, a beaver might well be a kind of strange dog or a pig with a with perhaps a fish tail on its body, you know, a real hybrid feeling like it is, almost like it's a strange like dog mermaid. It might be in almost all respects a deer, like a creature with long legs and hooves. And it may also look like a strange and confused rodent with a great button seam running down its chest. It may even look like a weirdly serpentine lion.

So Rob has been sharing medieval and Renaissance illustrations of beavers with me for a couple of days now, and I really do love all of them. But I do think the one I like the most is the one that's just straight up a deer with hooves, except it has razor blades for teeth, just like the rectangular razor blades.

Yeah, yeah, this one. I had to go deep around this one because I was It initially came up in an image search and you know, I think it was maybe on a pinterest or something. I was like, I can't trust this. But I eventually looked it up in the catalog of illuminated manuscripts and it is a Northern Italian illustration from somewhere around the year fourteen forty. And yeah, it just looks like a It is labeled as a beaver, but it is in all respects a deer. So I was just really astounded, like here, especially as an image, that it not only gets the form wrong regarding the target organism, it gets everything about like the energy of the creature wrong, you know, because it's it's one thing if you have a depiction of a rhino that okay, it's like a big armor plated thing with four legs. It's like, all right, I mean that's it's an extravagant version of the truth. But this, it's like, how wrong did this game of telephone go?

Right? With the right? You like, with deerors rhinoceros, you can see that beginning as a rhinoceros, but with embellishments, yes, But with the beaver, it's like, oh, I'm sorry, did you say beaver? I thought you asked for a depiction of a of a lion with a snake neck biting its own genitals.

That's right, because and this is this is something we'll probably get into mostly in the next episode, But there is this pervasive myth that existed for a very long time that when pursued by hunters, a male beaver would chew off its own testicles. And so many of these images. Be your creature more dog or catlike, or or actually just a deer with razor sharp teeth, it is often depicted nine at its testicles. That at least we have some answers for in the next episode where that idea comes from and why it's so pervasive.

Right, So you've got to stick around for next time to hear that.

Yeah, so let's start with what we know. Let's start with the reality. We're gonna start by talking about just basic beaver anatomy and behavior. And I probably don't have to tell most listeners out there what a beaver looks like. I mean, for starters, like, we have images all over the place of them, we have documentary footage. Many of you can go and see a live beaver at least in some sort of like a zoo environment, or you have seen them in the past. But on the other side of the coin, it's, like I said, still kind of have to tell you what a beaver looks like because the beaver is kind of in the same category as the spouting whale, as we discussed in some of our recent whale episodes, those particularly the ones on spouting and spouts. Because despite all this access to actual, solid documentary footage of the beaver, we still have this rich history of cartoon depictions of beavers that inevitably cloud our understanding of the creatures.

I mean, I think you get a fairly accurate mental picture if you just cross a squirrel with a grizzly bear. You know, you mash those two up your most of the way there. But while that does get you sort of the shape the outline, right, that does not tell you everything you need to know about beavers. Beavers are much stranger and more beautiful than I realized.

Yeah. Yeah, there's a lot of weird and wonderful aspects to their morphology, to their behavior, and a lot of this is stuff that our popular conceptions of the beaver don't get into. I mean, you know, they do get some of the things right, you know, the basic shape of the beaver is far better in cartoon than it is in many of these eliminated manuscripts. You know, some things hold up. Obviously, beavers are not going to sell you out to the White Witch. That's absolutely true.

So C. S.

Lewis was right on that count, even if he got the whole diet of the beaver wrong, because in Narnia, apparently beavers like to eat fish and chips. That's not happening in the actual natural world.

On the other hand, I will say, there is the kind of food and organism usually seeks out to eat in its environment, versus what an animal will eat if given the opportunity. I kind of wonder. I feel like if you gave a beaver a basket of chips and some malt vinegar, I don't know they might get into that.

All right, Well, let's start with the basics here. So beavers are rodents, and are in fact the second largest extent rodent, surpassed only by the mighty capybara. Beavers can weigh up to fifty kilograms or one hundred and ten pounds. There are two extant species of beaver. There's the North American beaver or castor canadensis and the Eurasian beaver caste or fiber. But the Castoridae family includes some impressive extinct species as well. In fact, there were giant beavers that lived during the Pleistocene, reaching weights of up to one hundred and twenty five kilograms or two hundred and seventy six pounds, So that is more than twice as big as extant beavers. Though I was reading they seem to have had smaller brains, among other morphological differences. But yeah, so they were bigger, and you know, maybe to some extent they didn't have to or had not yet developed these very impressive behaviors and abilities that we'll get into concerning modern beavers. Now, one note on these guys. They were still smaller than the fifteen hundred kilogram or thirty three hundred pound giant pacaranas of South America. Extant pacaranas only get up to light thirty three pounds or fifteen kilograms, and they can still be found in the western Amazonian River basin. But the giant ones, they were pretty massive. A lot of rodents of unusual size in freehistory, all.

Right, So no beavers today in that territory, but beavers can still get pretty chunky.

That's right. Yeah, they're pretty big, And this is like a fact. I frequently forget that they're the second biggest rodent. The kappy bear is easy to remember, but it's sometimes it's easy to forget who's coming in second. Now, it's extremely important to note that beavers are semi aquatic, having evolved to thrive in various freshwater habitats, so a number of the things we're going to be discussing about them line up with their habitat. For instance, they can hold their breath for fifteen minutes. They have transparent third eyelids called nicitating membranes to aid them in their swims, much like manatees. They also famously have long, flat black tails. We know this from the cartoons obviously, and these aid them in their swimming, but they can also use them to sound an alarm by slapping the water slapping the surface of the water, and they also use them to balance when they're carrying wood or other loads across the ground. For any of you out there who watch a lot of animal videos on Instagram and so forth, you may have seen videos of adorable beavers carrying carrots around and if you're not looking closely enough, you might think they're dragging their tails, But if you will look closely, you can see that the tail is off the ground and it's helping them balance.

One of the things I've noticed about watching beavers try to move objects around is how much more gracefully they do it in the water than on the land. So these are semi aquatic mammals, but I don't know, it seems to me that the water is where they're really in their element. They can swim fast and gracefully, even carrying like an unwieldy branch that's kind of unbalanced or something. They do that all quite well in the water, and then once you see them sort of toddling along across the dry land that it looks much more comical and awkward.

Yeah, and this is going to be important to keep in mind when we talk about the amazing ways that they transform an environment to better fit their needs and desires. Oh but before we get into that, we of course have to talk about the teeth of the beaver. This is something that is generally an important part of cartoon imagery concerning the beaver. A lot of times cartoon beavers will speak with a kind of whistle in their voice. But we also tend to get it quite wrong.

Okay, so I'm trying to picture the cartoon beaver. I think what we always see is an overbite with two kind of square shaped teeth grouped right together in the middle, like a person's front two teeth, but large and overlapping the bottom lip. Is that about it?

Yeah? Yeah, pretty much.

The truth is much more shocking.

Yeah, yeah, they have these. You know, if you look at a skull of a beaver, it's pretty markable because it's like this, the really kind of exaggerated rodent skull with just incredible incisors, you know, with these these two big shovel like teeth coming down from the top, two big shovel like teeth coming up from the bottom, and then the rest of the the back teeth or much further back, you know, giving them some ample room to do the kind of woodwork that they need to do with those chompers.

The skull is a powerful bone hinge, and it's like it's like a kind of alien biotechnological set of bolt cutters, except the bolt cutters are orange teeth.

That's right, The orange is key. This is something I almost never see in like a cute c illustration or a cartoon depiction of a beaver. So, yeah, these teeth have thick layers of enamel, which has this orange colorization because while other rodents boast magnesium enriched tooth enamel, beavers have iron enriched enamel. They're like, I mean, it's it's like something out of a comic book, right. The iron makes their teeth stronger against this the pure mechanical stress that they put them through. We should also note that these teeth continue to grow throughout their lives, to the point where they have to gnaw them down on trees to keep them down. But yeah, they're just super resilient, always growing, and they're also more resilient to acid as well based on their composition.

Just some tough, rusty looking teeth.

Yeah, yeah, the orange is really quite shyy okay. Another essential biological aspect of the beaver before getting into their behavior, is that they have a cloaca. So most mammals do not have a cloeca. There are some exceptions, you know, you look at the monotremes, golden moles, marsupial moles, ten rex just a few examples, but mammals have most lost these general purpose openings over the course of their evolution, but in beaver's they seem to be present as a case of secondary evolution, perhaps as an adaptation I've read against. It may have to do with the watery environments they find themselves in, protecting themselves against infections that might occur due to the state of that water. But it's also something and this will become important, I believe in the next episode as well. It can make it difficult to sex a beaver, as males and females look pretty much the same, unless the female happens to be pregnant or nursing at the time that you're trying to sex them. And when I say you, I of course mean people who have authority and expertise to be out in the wild trying to sex a beaver. You know, leave it to the professional biologists.

Leave it to beaver scientists. Yes, so these.

Various features aid the beaver in its primary enterprise of ecosystem engineering. We all know that beavers build dams, you know, this is, of course is true of the cartoons. But what does that really mean? Why? Why are beavers building dams? What are they accomplishing, So they actively alter their ecosystem via the blockage of rivers and streams with structures of like you know, sticks, mud, chunks of trees, that sort of thing, all cobbled together to dam up the water, and this allows them to create new lakes, new ponds, whole floodplains. Meanwhile, the lodges they construct for themselves are also made out of this kind of stuff, branches and mud and so forth, and they can only be accessed from underwater entrances in their constructed ponds.

Yeah, so this is something I don't know if I realized before. I think a lot of people assume that beavers live in their dams, but I think the better way to think about it is beavers construct dams in order to block waterways, which causes the area upstream of the dams to deepen and have a more lake like environment rather than a flowing river or stream. And then in that flooded area that is where they build the lodge they live in. So they sort of create a flooded area which can it can serve multiple purposes, one to house the lodge, but then also they can sort of dig out from there. I think you're about to mention something about this.

Yeah, they're a lot like humans. Human beings do this with their modern technology. They come to say a dry desert environment or a swamp environment, and they're like, you know, what would go great here? What I would like for my purposes of living here. I'd love it to be just like a nice little park with some nice grass, you know, and maybe a few trees. I'm going to change everything so that it fits my needs. So the primary purpose for the beaver dam is to create a protective body of water for that lodge, making it even more difficult for predators to get at them. And even if predators were to get to them, they have that underwater escape route in the event of an attack. That's the that's the only way in and out now. It's worth noting, however, that especially in parts of Eurasia, beavers don't always have the same predator threat they once did. But they build anyway because no one told them not to. And also, more seriously, like, even though they are not predators now, I mean that's you know, any kind of evolutionary change would occur over a much vaster period of time than the removal of their predators.

Amounts to right, So an environment full of say like gray wolves and bears may have shaped them. And even if there are many fewer of these predators than there once was, that they are still the animal made by that world.

Right. For instance, they're still certainly nocturnal creatures. I mean they're also active, you know, dusk and dawn a little bit, but during the day proper, they're inside, they're resting, and part of that is to avoid predators. Now you mentioned earlier, Joe that you even just looking at videos, you can tell that they're more awkward on land than they are in the water. And that's of course another big important aspect of their damming of waterways, creating this sort of vast flood plain, like turning a stream going through a forest or something to this effect into kind of a flooded forest environment. This opens up speedy water routes back to their lodge. From perspective, feeding grounds.

Yes, sort of the same way. You can imagine it like humans creating roads, like paved roads between say the farms that they work during the day and the houses they live in. But beavers would do this by instead creating flooded areas. Especially they can sort of like dig out channels along the bottom that the water from these flooded areas can run into, allowing them to have a sort of canals like roads made of water where they can move quickly, where they can move submerged, which is safer and better for them than trying to move awkwardly over land.

Yeah. Now, in doing this, of course, they alter the ecosystem local ecosystem in a major way, opens up opportunities for various other organisms as well, and also discuss some of the potential downsides at least for some organisms in a bit. But at any rate, this cements the beaver's place as a keystone species. Beaver's just just completely change the immediate environment, produces more open water, higher water tables. And yeah, it's this entire system they have going for them here. It's just so fascinating. You can if you look online, you can find some some side profiles, some cutaways of what the lodge looks like, and it's pretty ingenious. It also serves as a place for them to store food and even provides refuge during frozen months. They don't hibernate properly, but they can hold up in there.

One of the things I've read about is that they often can store lots of food, so they're vegetarians that eat actually like you know, parts of trees, vegetation from all around them, which they can keep stored in the world water underneath the pond created by their dams, and that's an interesting thing. They can raise the water level in order to help protect areas of food storage in the water for the winter, because by raising the water level, they create more area underneath that won't freeze over when the weather gets cold.

Yeah, and these lodges and dams that they can even though the beavers themselves tend to only live about I think eight years max, a single lodge and dam can be maintained over generations, so the lodges may end up with like several stories to them, and the dams can get quite massive. There's an Alberta area dam that was built apparently in the nineteen seventies. Initially wasn't discovered till around two thousand and seven because it's just out in the middle of nowhere. It's not like in downtown Alberta. It's like out in the boonies and it's thought to be the world's largest beaver dam known beaver Dam anyway, covering a good half mile. There's actually an Alice Obscure article about it. If anyone's interested. Just look up world's largest beaver dam and you can see some like aerial photographs.

You know, something interesting I was reading about was the role of beavers in maintaining ecosystem health by allowing for a greater diversity of different types of plant life to thrive. I think sort of in the same way that forest fires you might think of them as purely destructive. Of course they are destructive, but you know, forest fires occur naturally all the time, and when a forest burns, that creates sort of new opportunities for new types of plants and other life forms to thrive in a place that was once covered up by you know, a lot of tree canopy. So in the areas around beaver dams and lodges, they will clear out lots of the trees. They literally chew them down and they'll fall, and you know, the beavers will do what they will with them. But this creates all kinds of opportunities for other plants and other life forms that wouldn't normally thrive in the forest to have a shot.

Yeah. Yeah, the paper that I came across was talking about sort of like the pros and cons. I have another one I'll get into about some of the potential benefits, but just to give you a full idea of sort of the rodent altered landscape we're talking about here, I was looking at a twenty fifteen paper published in IOP conference series, or presented in the IOP conference series Earth and Environmental Science. This one is This was by Raskova to Mina at All, and they talk about some of the positive and negative consequences, at least initially stressing some of the negatives maybe that are not at least instantly discussed as much. But you get soil overwetting obviously, because you're getting flooding occurrently it occurs. You also can have water stagnation that results in lack of oxygen, high carbon concentration, and the death of many aquatic organisms. And then the flooding can also cause vegetation death. But at the same time, the authors who are stressed that it can result in a rise in the biodiversity of water organisms. So you know, they're changing everything. They're changing the balance of the local ecosystem, and it's creating a lot of opportunities for new things, but it is also cutting things short for things that we're living there already. Now, a really interesting study that I came across this was a twenty twenty two Stanford study by Dewey at All published in Nature Communications, And in this paper they point out that beaver habitat ranges in the US are going to continue to widen with warming temperatures driven by climate change, but the benefits of their dam building will actually quote overshadow climate extremesquote. So this is not to say beaver dams will cancel out climate change or anything like that, but in some respects it kind of lessens the blow. Specifically as far as water quality in mountain watersheds are concerned. Dams can raise water levels upstream and divert water into soil and surrounding waterways, and this ends up sort of, this ends up like creating a robust filter system, a filtration system for excess nutrients and contaminants for the water before it passes on downstream. So today beaver's in North American eur Asia are both doing great. They have bounced back from near extinction due to hunting, and we may touch on some of that a little bit more in the next episode, but because there are a few different reasons that have driven beaver hunting over the years. But to go back to speaking of their construction of dams and their changing of the environment, there's another great illustration I came across by Nicholas de Fer who lives sixteen forty six through seventeen twenty, and this is just a small scene from a larger map. He was a French cartographer, so this is just you know, filling in some of the blank spaces, like we've discussed before on some of these older maps. But this illustration shows beavers at work. They are downing trees and they are dragging off the wood to build things. There are the beavers themselves look largely accurate. There may be a little more bear like, but the basic morphology is there. The main problems here are that, first of all, there's like, you know, one hundred beavers in this in this one image, like they're working as an army. And then also like clearly there wasn't a lot of detail on how they carry the wood, because the central beaver that you see is standing up in a bipedal posture with an armload of wood. Thrown over his shoulder like a human being.

Yeah, yeah, like a Paul Bunyan carrying an axe.

Yeah. But I like the spirit of industry that they captured here, despite some of the ridiculous details, and again a huge improvement over some illustrations from previous centuries.

I wonder, is this one of the maps we looked at in our horror Vakay episodes where we were talking about maps with excessive illustrations.

I don't believe it is. I looked at a bigger version of the map and I almost included it in our notes, and I don't think I had seen it before. It was a map that it's known as the beaver map and has to do with the locations of beavers because it has to do with the hunting of beavers, which again was quite a big industry for a while there, so big that it just about wiped them out. So the large semi aquatic rodents have come to flood the world and to remake it according to their designs. But the weirdness and the complexity doesn't stop there. Joe tell us a little bit about beaver society and about beaver tool use.

Yeah, Rob, I think you found one of these papers first, and that's what started this whole. But I got lost on a going down a rabbit hole or maybe a beaver canal, trying to search out examples of possible tool use documented in beavers, and in fact, there are a few very interesting different observations corresponding to each of the extant species. Beavers clearly are an interesting type of animal to look at for signs of tool using intelligence, since they are masters of manipulating their environment through the dams and the lodges they build. Though I think it's interesting that nest building is often not typically thought of or not sort of front of mind as an example of tool use. And there are different examples that different zoologists or animal behavior experts will use to try to define tool use. So in the papers I was looking at, a few different standards were cited. One is a definition of tool use by a researcher named Alcock, who says it is quote the manipulation of an inanimate object that improves the organism's efficiency in altering the position or form of some other object. So, you know, using an inanimate object from the environment to better alter the former position of something else. Another definition I've found cited. This is from Beck in nineteen eighty quote the external employment of an unattached environmental object to alter more efficiently the form, position, or condition of another object, another organism, or the user itself, when the user holds or carries the tool during or just prior to use, and is responsible for the proper and effective orientation of the tool. Now, I appreciate all of the conditions on that, because I think it is important for people to be specific about what they're talking about when they look for examples of tool use. But I also wonder, once you're specifying that many conditions, is the category of tool use becoming more or like a function of the definition you lay out than than a fundamentally different type of activity itself than some other activity that that wouldn't quite fit this definition.

Yeah, I mean, and sometimes we can almost get too hung up, I think, on the on the the idea of tool use and the definition of tool use, because we'll look at the most complicated burden, nest or bower that you can imagine and will be like, well, it's intricate, it's amazing, it's beautiful. But have you seen this monkey stabbing a smaller monkey with a stick. You know, it's you know, you know, it can almost you can almost set it up as this this thing that is the thing that we do. You know, that is a very there's something very human about tool use, and you know, obviously a huge, huge aspect of human life and human development. But but yeah, it's it seems like at times a lot of extra mental gymnastics is it has to be, it has to be utilized in order to even discuss it.

So I'm not going to get super hung up on definition of tool use or what really counts as tool use today. We've talked about some of those debates in plenty of episodes in the past. Instead, I'm just going to talk about some studies describing specific behaviors, and you can make up your own mind about whether it seems like tool use to you. So the first thing I want to talk about is an older observation. It's older than either of the two papers that I'm going to discuss here, but it's cited in the first of them, and I'll get to that paper itself in a second. But the observation is that a researcher named Georgio Pilleri observed something interesting while studying two captive beavers at the Burn Brain Anatomy Institute in nineteen eighty three. So the beavers were living in a concrete pool that was supplied with a constant flow of fresh water, and overflow of this pool was routed away through a series of three drain holes, each zero point eight centimeters in diameters, so little holes in. The beavers had been given a supply of sticks and twigs to do what they wanted with, and for some reason, what they did is they selected and cut three sticks from their supply to the exact dimensions needed to plug the tiny drain holes that where water drained away from their pool. And this completely stopped the flow of water away from the pool. Now what's going on here? At first, it was kind of hard for me to believe this would be fully intentional behavior, as in, like the beavers understood that they were plugging the drains to stop the flow of water from their enclosure. But then I thought, you know, I guess I wouldn't be surprised if beavers have like a sense for detecting gaps in dams and plugging them, Like maybe they're good at sensing. My first instinct was maybe they sense like the delta pee. You know, the difference in pressure, like when water from a large pool is flowing out of a small piper hole and you could feel that pressure that would like get your hands stuck to the hole if you held it there, or which in larger scenarios can be of a great danger to divers. You know, you don't want to go near like the intake hole at a dam, if you're diving near it. I thought maybe they sense the delta pee, and so they sense that and they naturally want to plug it up, But I didn't know. However, I then sort of came across an answer. So I was watching a segment on North American beavers from BBC Earth narrated by David Attenborough, and this documentary segment captured a scene of beavers finding a leak in their dam and then getting right to work retrieving wood, vegetation and clumps of sediment down from the bottom of the pond to plug up the leak in the dam where water was running over the top. And Attenborough, in this documentary segment narrates that beavers are thought to detect these leaks by hearing the sound of trickling water and when they do, they begin repair work almost immediately. It seems to be fastidious, almost compulsive. This compulsive desire to fix the holes when they hear the water trickling, and this would make the drain plugging behavior in the concrete enclosure in the eighties make a lot more sense. So I decided to look into this further to see if this was indeed true to some degree. It seems it is, and so I didn't have time. This was soon before we started recording. I didn't have time to find the primary reference on this, but I did find a good twenty fifteen Gizmoto blog post by Esther inglis Arkell writing up summarizing the research of a Swedish zoologist named Lars Wilson who studied beavers back in the nineteen sixties, and according to the summary, Lars Wilson found that dam building was instinctual rather than learned, and the way Wilson identified with this was that if you took young beavers and you separated them from their parents at birth, they would still build dams basically the same way, using the same techniques as their parents, even though they were clearly not having the opportunity to be taught to do that. So it seems based on that at least this is probably a routine behavior. It's based on beaver DNA. They don't have to be taught. But Wilson also found that beavers didn't always build dams. In environments with still water or only very gently moving water, dam building was not a priority. The beavers would just maybe they like dig a hole in the mud and just chill there, you know, they just wouldn't build. And so by manipulating different variables, Wilson identified the sound of trickling water as the primary trigger for dam building, even to the point of a discovery that this was the part I found most fascinating. If you put a speaker in the beaver's enclosure and you played the sound of trickling water through it, the beavers would go to the speaker and start building on top of it. They would start piling up sticks and mud and branches over the speaker playing the sounds. They were trying to plug the speaker to make it stop leaking.

Oh my goodness.

Wilson also found that if outflow pipes, so you had a place where there was actually water leading away from the pool, but you carefully designed the pipe so that they made no noise, the beavers would not be able to find and cover them. So this might lead you to think, okay, so like the louder the rushing of the water, the more beavers want to make a damn there. But it also seems like it's not quite that simple, because I was reading a news article from the Harvard Graduate School of the Arts and Sciences called Damned If They Do by Paul Massari. This article profiles the research of an environmental engineer named Jordan Kennedy who has done research on beavers and their dam building practices and the environmental effects thereof. And Kennedy says that it can't just be about the like the magnitude of sound of moving water, or beavers would be trying to build dams across Niagara Falls, you know, just like loud, violent, rushing waters where building would be totally impractical. So instead, there's got to be a kind of Goldilocks zone for dam construction, something that the beavers naturally detect that allows them to know, Okay, this is about the right amount of flow to try to dam up.

Yeah, yeah, damming up Niagara Falls, like obviously, that would be great like, that's kind of like the beaver fan fiction. That's the pipe drain, But is it practical. No, you need to have that just the right environment that can then be manipulated to make the ideal environment for the beaver.

Right, So, the author of this article writes, quote, the water in a beaver's habitat needs to be a certain depth, for instance, to keep a food cache from freezing to the bottom in winter and to enable them to evade predators. The plants that beavers prefer to eat flourish best when water flows at a certain velocity. So you're looking for this goldilocks zone, an area of a certain amount of water flow, maybe a certain narrowness of the channel or certain depth of the channel, and that's the place where you want to dam it up. And beavers apparently they locate that. A big part of the sense data informing them of that area appears to be sound. Maybe maybe the overwhelming part of it is sound, but there may be other cues as well, and so I don't know. I thought this was so interesting, and I'm just trying to imagine what it's like to be a beaver, to have this powerful instinctual drive to plug leaks. So imagine the same kind of base level instinctual drive that humans might have for sex, or for food, or to care for children, all the like the most powerful drives in our brains. But there's a drive like that to hunt down the source of anything that sounds like trickling water and to just plug it with junk. You know, I don't know. That's like, that's another that's another type of mind experience, a relationship to the environment.

Wow wow, yeah, Like what would yeah, how would like we can't help but extrapolate that into like a human like intellect and human like culture, Like what would advance beaver civilization be? Like would they actually go after like complete inundation, like a complete flooding situation, the destruction of all naturally occurring waterfalls, or would they just kind of dream about it? Or what would their TV shows be? Would it just be like countless channels of leak plugging and so forth.

The speaver thought she had it all, but then she heard the trickle and couldn't find it searching, Like all dramas begin with the conflict of hearing a trickle.

That's the call to adventure.

Yeah, but anyway, all that stuff I just read about got kicked off because I was reading that anecdote about the findings of Giorgio Pillari in nineteen eighty three, which was cited in a paper by D. M. Barnes called possible tool use by beavers cast Or canadensis in a Northern Ontario watershed published in the Canadian Field Naturalist in two thousand and five. So this is one of the main two papers I was looking at about possible cases of tool use in beaver's Barnes says that this report is based on evidence relating to the North American beaver that's Castor canadensis at a remote damn site in the Chapleaux Crown Game Preserve in northern Ontario. The author says, at this location they found a clump of willow stems, so like little small tree trunks that had been cut by beavers. But the fascinating thing was they were cut at the extraordinary height of approximately one meter off the ground. Beavers are not that tall normally, these beavers cut at an average height of about thirty centimeters, so the beavers were chomping off these willow trees at three times the normal height they could reach with their teeth. Barnes writes, quote, I made a careful examination of the area and found that there was no apparent way the beavers could have cut the stems at such a height. When I studied the willow clump more closely, I noted that there was a freshly cut willow stem approximately twelve centimeters in diameter, leaning against the main stem of the willow clump. Its approximate angle was forty five degrees. In addition, I observed cutting at both ends of the leaning willow segment, and then there was a There was a photo accompanying this in the article. Now, at first the author thought that, okay, so this is a log propped up forty five degrees against the tree that is cut off very tall. The author thought maybe this log there had simply fallen that way. I don't know, it's something that the beaver cut and then it fell. But that's impossible on further examination, because the log was clearly from a different tree than the stem it was leaning against, like there was different bark texture and color and so forth, and its position just did not seem plausible if it had fallen from above. Another possibility the author considered was that these willow trunks had been foraged while there was heavy snow on the ground in the winter. So maybe the beavers were able to reach a meter up the trunks of these trees by crawling around on top of the snow. Okay, but the author things that's really unlikely. Given the position of the willow clump relative to the beaver dam and lodge and its entrance and exit. It seems it would have required a major overland journey by the beavers on the top of the snow in the winter at a time where this just would not fit with their normal behavior. Instead, the author suggests that maybe what happened here is the beaver used a prop. The beaver used a piece of a log that it had cut off at both ends and propped it up against the base of the trees, and then climbed up that and was able to chew off the willow stems at an upper level rather than a lower level. Now, why would this even be beneficial? The author says this would be probably to reduce foraging time. So the longer you forage number one, the more thermal stress you're exposed to not being the right temperature. But more importantly, the longer you are exposed to predation. Apparently beavers do not like to spend a lot of time out on the ground out of the water, so they are trying to hustle as fast as they can whenever they're out there cutting, and in this case, apparently using a cut stem to climb up the willow trunks to access a higher up part of the tree to chew through would have meant that they had to spend less time chewing and less time cutting all right.

Like a little bit higher they just it's gonna be less, it's gonna be a narrow or bit of wood to shoot through.

That's what I assumed. It didn't specify exactly why cutting higher up was reduced foraging time, but that was my interpretation.

I could be wrong, and that's why they potentially could be using essentially a beaver ladder, a beaver bit of scaffolding.

Right, But we don't know. This is just one observation. And also they didn't see them doing it. They just found this strange piece of scaffolding there later.

Yeah, more mysteries related to I mean, I guess this is kind of cutting into some of the mysteries involved in these wildly inaccurate depictions of beavers is that these are creatures that live often in very rural situations, far from human activity. They're probably doing it at night, and they're spending as a little time necessary doing it out where other eyes could see them.

Right, okay. Second paper I came across alleging possible tool use behaviors by This is called tool use in a display behavior by Eurasian beavers or castor fiber in the journal Animal Cognition by Thompson at All in two thousand and seven. So here the authors write that documentation of tool use is relatively rare in rodents, and prior to this paper there were no documented cases they knew of of tools being used by rodents in what are called agonistic displays. Now, agonistic is a word used in the study of animal behavior to describe conflict or fighting. So an agonistic behavior is not necessarily fighting itself, but also could include social behaviors related to fighting. So these would include threat displays trying to, you know, look big or otherwise intimidate another animal, displays of aggression, as well as things like submission or retreat behavior. The authors of this paper say that in their field observations of the Eurasian beaver. They witnessed the behavior that they call stick display, which they interpreted as an agonistic display behavior. And what this consisted of is beaver would go pick up an object, usually a stick, whenever a stick was available, and then it would rise up on its hind legs and then move the upper body rapidly up and down while holding the stick or other object in its mouth and front paws. And Rabbi attached a picture for you to look at. They had a photo of this. In this photo of the beaver is in the shallow part of a waterway. It's standing up on its back legs. It's kind of I don't know how to just it's kind of like roaring posture. But it's got a big old stick in its mouth, and it's gripping the stick with its two four paws, and the water is splashing all around as the stick I guess, rapidly dips in and out.

It's impressive and it's frankly a little intimidating, this beaver saying, behold, look at the feats of strength. I am capable of.

So several observations about this behavior. First of all, they say, beaver's only picked up these display sticks or other objects at the same location where they were used, and they were never seen modifying the objects, so it wouldn't It wasn't like they would carry a stick around and then use it in a different location or modify the stick in any way.

So, for instance, compare it to like human tool use that we've discussed in the past rocks. This would not be on the level of picking out favored rocks for throwing at other humans, polishing them, changing them, etc. This would be more on the level of when threatened, you might look down, grab a rock and use it. Though of course, in this case, the beavers are not hitting each other with the sticks allegedly, the hypothesis here is that they're using them as a pure defensive display.

Right. Second thing, This often happened in shallow water, so the shaking of the stick would cause splashing in the surrounding water, but occasionally it also took place on dry land, such as in weeds, where there was no significant sound produced. So the authors think because it took place in both scenarios and when it was on dry land it didn't really make a noise, they think it is primarily a visual signal. An important bit of context is that Eurasian beavers are territorial. They live in family groups with usually a dominant breeding pair and then assorted offspring of that breeding pair. And they defend the borders of their territory from encroachment by other beavers. So they mark their territory by scent. This is done with secretions from the anal glands or castorium. Which castorium, I believe, we'll talk about more later in the series in part two allegedly smells like vanilla, but we'll come back. When rival beavers come into a family group's territory, the home turf beavers will react first of all with tail slapping. Rob you mentioned this. This is a loud signal that beavers make by repeatedly smacking the water surface with their tails. This is also used to alert members of the family group when a predator is cited. They also respond to unwelcome presence by visual displays or sometimes with actual fighting, though physical fights are relatively rare. The observations carried out in this study were conducted on wild Eurasian beavers in southeast Telemark, Norway. Overall, the researchers observed one hundred and thirty one cases of stick display behavior that met the criteria for inclusion in their study by four adult males, two adult females, and five unidentified animals. However, it seems that some individual beavers engaged in stick displays far more than the others.

Quote.

It was clear from our observations that one female beer Git and one male Froda were the main performers, with a contribution of fifty one point nine percent and thirty five point nine percent, respectively, of the total number of stick displays observed. So what does that add up to. It's like eighty seven percent of stick displays were from two beavers.

Wow, go Froda.

The real champion is beer Get here. She's got more than half of them just under her belt.

Yeah yeah, I mean really, beer Get needs to get get most of the credit here from Froda doing pretty well as well.

So they say, stick displays happened almost exclusively at the borders of beaver family group territory, and most displays appeared to be directed at rivals. The displays were often preceded by scent marking, so this kind of suggests it probably is being used as an agonistic display. However, this behavior, while common in the groups observed in this study, is not necessarily generalizable to the total world population of these beavers. It has not really been observed in beaver's generally across the full range, suggesting it may be specific to certain populations.

Wow, like even like some sort of like localized beaver culture.

Yeah, maybe apparently something. At the time of the study, the author said there were some isolated reports of similar behavior in a few North American beavers, but not most, and it was not found in all Eurasian beavers either. So the authors argue that stick displays might be especially favored in high pressure situations. From reading their description of the area, it seems like the groups observed in this study might be in especially crowded beaver territory, where like, you know, the areas around different family dams and lodge sites are sort of all butting up against one another. They also observed higher rates of stick displays in springtime, meaning it's possible it could have some association with breeding. But if the stick shaking is a genuine agonistic display behavior, the evolutionary purpose would probably be to convey honest information about the beaver's size and strength, so it's like, I'm big and strong. Look at how I can shake this stick. You don't want to bother actually getting into a fight with me, right, we don't have to do this.

I like these sort of levels of communication that seem to exist between beaver groups here. You know, it's like, at the end of the day, all beavers really want to do is build things and plug holes. Uh. You know they have they have a lot of hole plugging to do. They have they have a lot of work to accomplish. They don't really have time to get into these fights. These fights are just would be destructive. Uh So instead, let's just make sure that we're very clear about how everyone feels about these these border scenarios, and uh, if need be, let me just show you, give you a taste of what could happen. Just look at this stick lifting ability here.

The neighbors are getting nosy and beerget shakes a branch and it's like, no, don't make me do it. Don't make me do it. And it seems most of the time they're like, Okay, I won't make you do it. Bergeit, man. I think we've got to be out of time for for part one of Beaver's here right, But there will be more.

Yeah, in the next episode, we're gonna we're gonna get back to that idea, that that false idea of beaver whilst being hunted deciding to chew their own testicles off again that you see various examples of, particularly from like illuminated manuscripts and so forth and bestiaries. We'll come back and to discuss that, plus who knows what else we'll uncover about beavers in our research. In the meantime, we'd love to hear from everyone out there if you have any especially since a lot of times we do these Tuesdays to Thursday. This one's going to be a Thursday to Tuesday, so who knows, you might be able to get some really core beaver facts and beaver experiences into us before we record the next episode. You know something you've picked up somewhere or just you know, accounts of observing beavers in the wild. I'd love to hear about that. So, whatever your feedback, whatever your thoughts, share them with us. We would love to hear from you. Just a reminder that Stuffed to Blow Your Mind is a science podcast with core episodes on Tuesdays and Thursdays, So look for those in the Stuff to Blow Your Mind podcast feed wherever you get your podcasts. On Mondays we do a listener mail episode. On Wednesday's do a short form artifact or monster fact episode. I know sometimes people say I wish they were longer. Well, they're short. That's part of how it works. But occasionally we're gonna put out We're going to continue to experiment, experiment with putting out omnibus episodes that may take up like multiple related monster facts or artifacts, and put them out so periodically you'll get a longer one in there as well. So yeah, let us know if you're liking that, and we can keep doing it. Oh and then on Fridays we set aside most serious concerns to just talk about a weird movie on Weird House Cinema.

Huge thanks to our audio producer JJ Posway. If you would like to get in touch with us with feedback on this episode or any other, to suggest a topic for the future, or just to say hello, you can email us at contact at stuff to Blow your Mind dot com.

Stuff to Blow Your Mind is production of iHeartRadio. For more podcasts from my Heart Radio, visit the iHeartRadio app Apple Podcasts or wherever you're listening to your favorite shows,

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