NatureBoost Episode 61: Beavers
February 2025
SMA
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>> Hey there, and welcome back to NatureBoost! I'm Jill Pritchard with the Missouri Department of Conservation. During one of the first NatureBoost giveaways, I asked you guys what things you wanted to learn about in an episode, and one of our listeners really wanted to hear more about Missouri's beaver population. I remember chuckling when I read her suggestion, because it struck me as a little random. I'd never given beavers much thought, maybe because I'd never seen one . . .? Obviously, I know they build dams. That's what they're most famous for. But after doing a little research, I learned about the tremendous impacts they have on the health of streams and rivers, and how they create new habitat for plants and other wildlife.
Furbearer biologist Nate Bowersock joins us again to tell us more about "nature's lumberjacks."
[Music ♪]
I'm going to hop right in, if you're good. . ..
>> Yeah, let's just do it!
>> I've never seen a beaver. [Laughing.]
>> Really?
>> Other than on TV, I've never seen one in real life.
>> Oh man, Jo! We gotta get you out and go find one!
>> I would actually like that! Can I tell you a story? So, whenever I first started working in MDC, we have the trails around here, and there's a pond out there. And there's a bridge over the pond that I was walking over. I was looking at the water, and something was swimming in the water, and I got so excited. I'm like, "it's a beaver!" But it wasn't!
>> It was a muskrat, wasn't it?
>> [Laughing.] You already knew! Yeah, it was a muskrat. I felt silly, because that tail . . . it does get confused with muskrats, right?
>> Oh yeah! Oh, yeah. And then, you know . . . maybe we'll get to it eventually, but you know, there's also nutria out there.
[2:01.]
>> Nutria? Is that how you say it?
>> Nutria, "new tree uh". . . [unclear.] Yeah. They're bigger than a muskrat, still not quite the size of a beaver, but all three have very similar characteristics. It's just the size and the tail; that's the varying factor for sure.
>> So, a rodent. A beaver is a rodent.
>> Yeah. All three of those are species of rodents, but beavers are a rodent, they're our largest rodent in North America.
>> That's kind of crazy to think about. They can get fairly big.
>> Yeah. They can get almost to 100 pounds, which is wild.
>> That's insane! That's bigger than my dog. I always thought my dog was a massive monster. So, that's kind of freaky to think about, that they can get that big.
>> Yeah. And a big part of that is, they're adapted to chew down, knock down trees. They have all this muscle in their skull and jaw to be able to chew efficiently, you know? Think about a bear. A bear is so big, and they have the jaw strength to break femurs, you know? To chew into them. At the end of the day, a beaver is still not that big. If you look at the skull . . . it's built like this little tank, to be able to chew down huge trees.
>> Oh, they've evolved to be able to have that characteristic. Okay, so, before we get into taking down whole trees and the dam building, I want to get into a little bit about more of their physical characteristics. So, they're kind of interesting because they're semi-aquatic.
>> Yeah.
>> They're on land and in water, and they're pretty good swimmers. They've got those webbed hind feet, right?
>> Yeah. They're really well adapted to swim. I was actually just reading how their anatomy is. They're actually built more similar to ocean species, like a seal. If you look at their anatomy, they're built to shoot through the water more like a seal does.
>> Like a torpedo.
>> Yeah, kind of, which is crazy. They're not necessarily a fast swimmer like an otter, which is a giant, muscled animal that slithers through the water. Still, they can swim very well underwater, and stay under for . . . I think like 15 minutes or so? Which is just wild to think about.
[4:03.]
>> It really is! Now, they've got that big, flat tail. Does that help them swim, too? Or does the tail serve a purpose?
>> Yeah. Their tail isn't as much of a tool to swim with, you know? Again, I'll probably make references to otters, but you know . . . another semi-aquatic mammal species that we have here. But, you know, their tail is more, it's something used for communicating. Slapping the water . . . whether it's to tell other beavers that there's danger in the water . . . to try to deter a predator, you know? It's very surprising. If you're ever in the wild and hear a beaver tail slap, it's very loud.
>> It's loud!
>> You know, other times, if they hear a noise and don't know what it is, they'll also do that just to try to get a reaction, to get a better idea of what's going on around them.
>> Okay, very cool! So that big tail helps them with that. We talked about how big they can get. Another interesting characteristic of them, is their teeth. Their teeth never stop growing, right?
>> Yeah. They're always growing. It's actually one of those other adaptations of needing to chew on big trees. It's like that back-and-forth thing. They need big teeth to be able to chew hard wood, but at the same time from that, they're always growing. If they're not chewing on something, it could actually be a detriment to them. It's a balancing act for them. They have strong teeth so they can chew on big trees, but if they don't chew on big trees, it can be an issue for their teeth, because they are always growing.
>> And they're orange, too?
>> Yeah. They're really cool. They can be almost bright, neon orange in some cases, depending on the trees that they're chewing on.
>> So . . . really? That can affect the coloring?
>> Mhmm.
>> But why are they orange, anyways. Is that some type of iron thing?
>> You know, I'm not quite sure. That's a great question. We'll maybe dig into that later.
>> Interesting. I didn't know that trees can affect that, too. Okay, so, they're semi aquatic. I've never seen one. Am I just not looking hard enough, or what?
[6:00.]
Obviously, their habitat has to be near water, like rivers and streams.
>> Yeah. They tend to be primarily spending time in those areas where there is a stream system. They can spend time on a pond, but they're attracted to the noise of moving water.
>> Okay.
>> Then they find moving water, and if there's a substrate of material around, then they'll start building a dam, and inhabit those areas. Anywhere you have moving water, there's a decent chance of having a beaver. You know, a great place that you could go, close by to Jeff City here, is going to Eagle Bluffs Conservation Area. We have otters, beavers all over . . . and there's definitely a decent chance if you're cruising those roads and looking at different flow pools, there's definitely beavers that hang out in there.
>> Are they nocturnal?
>> They tend to be . . . borderline crepuscular to nocturnal. They tend not to be as active in the middle of the day, but then . . . dawn, dusk and even through the night, they'll be more active. Part of that is trying to avoid contact with predators.
>> Okay, I was going to ask if there's a reason for that. Okay. They're trying to avoid being predated upon. Okay. So, they're along that moving water . . . so, them cutting down the trees, are they feeding on the bark? Is that what they eat, or are they vegetarians?
>> Yeah. They mainly eat plant matter. So, they tend to eat . . . you know, plants that have kind of softer tissues tend to be better quality for them to eat. It's easier to break down, easier to digest. You know, they still eat the harder wood trees too, especially when they're close to the water. They'll chew those big trees down to help build their dams, and then they might even actually focus on the larger trees near the water, to make their dams. Then, go further away from the water to find the food sources that they prefer.
>> What I find so fascinating, whenever I was doing a little research on beavers, before we met . . . is the fact that they can cut down whole trees.
[8:00.]
And . . . surprisingly in very little time, too. Which, again, I guess goes back to what you were talking about earlier, that they're really adapted with that skull and muscle, to be able to do that.
>> It's pretty wild. Yeah. It's just continuous chewing at the tree, but the wild thing is, they have the ability to not only knock the tree down, but they can actually place it for like a forester or a logger . . . they have to put so much time into learning how to cut that tree down. Beavers know how to do that too. They know how to fell a tree in an efficient way, that if it's along the edge of the water, they're actually felling it into the water in the direction they need it, for building their dam.
>> I love that. They're efficient at that, and the placement of that.
>> Yeah. At the end of the day, yes . . . they're powerful rodents, but they're not that big. They can't lift up that huge, hundreds of pounds tree. So, why not down it in a way that you don't have to move it afterwards?
>> I just love that! Real intelligence there, to do that. A beaver in Canada cut down a cottonwood nearly 6 foot wide, and 100 feet tall.
>> That's just wild . . . yeah.
>> That's in our "strange but true" book about beavers. That's insane!
>> Oh, yeah.
>> Insane . . . yeah. Their capacity to do that is kind of mindboggling. Okay, so, that obviously brings us into discussing their most famous trait, obviously, the dam building. What is it about them that makes them want to create these dams? What's the big purpose there?
>> Yeah. That's a great question. You know, they build dams for multiple purposes. The first one is, yeah, they build a dam to create a pond. When they're in water, they're the safest. There's not many predators that can really go after them when they're in the water. Yes, otters are predators, but they rarely go after beavers, because they're so big. Otters tend to go for fish, and other animals smaller than them.
[10:01.]
So, animals like wolves or coyotes . . . they would like to get a beaver if they could. So, if the beaver is in water, it's better off. If you have a small stream, it's harder to hide in the water if the stream is shallow. By damming up the stream, slowing up the water, you're damming it up, creating a pond. Then, that provides protection for them. On top of that, once we get into winter time . . . especially in areas where it ices up, they'll actually bring food into those ponds, and put it under the ice, and it'll actually be a food cache that they can rely on. They can sit in their lodges, stay warm, and when they're hungry they can dive in the water, get a snack . . .
>> Heck yeah!
>> And you know what? Not even worry about going up to the surface and getting attacked by something. It's such a smart way to do things.
>> It's like squirrels stashing away their nuts, kind of.
>> Totally. But in this case, they're stashing in the water, and in this structure that they built themselves, which is just wild.
>> They're hunkering down, I like that. That's what I do every winter, too. I don't want to go outside either. So, do we know about how long it takes them to build a dam?
>> You know, I think it's dependent on the size of the stream, and the substrate that's around, you know? A smaller, shallower stream, it probably wouldn't take very long. I wouldn't be surprised if it only took them a night or two to build up a dam. Obviously, the bigger and deeper the water gets, the more energy it takes for them to build a dam. The wild thing is in many cases, it might be just a lone beaver that builds the dam. And then, once it's built, its family group forms . . . then maybe the family will help maintain it, especially when we have those big spring floods that could damage the dam. Then, the family might participate in maintaining the dam, but yeah . . . it's just wild. They can be very efficient, and build these things very quickly, even when the water is moving pretty good, or it's pretty large.
[12:02.]
>> So, are the dams a way to attract a female? Or . . . what's their mating like? Like . . . how does that work?
>> Yeah. My understanding is . . . we call them colonies, but at the end of the day it's just a family group. Just like a wolf pack, everyone says "it's a wolf pack, it's all these lone animals together." Well, no. Same thing with wolves . . . they're all related animals. There's usually a breeding pair, and then they have their pups, and then each generation helps raise the next generation of . . . kits, I guess it is. Beaver kits.
>> Okay.
>> Usually what will happen, especially if we think of a younger age class, you'll see a young beaver find an open stream area, or maybe an abandoned dam that other beavers had built in the past. And then, fix it up or build a new dam. Then, essentially, it's creating that home that they can use, and potentially another mate will show up, they'll pair up. From there on out, they'll breed, they'll have their kits and raise a family from there . . . the cool thing is, depending on the size of the stream and the amount of water that builds up behind their dam, they might build additional tiered dams down the way, to help with the overflow of the water. So, they have multiple places to slow the water down and be protected throughout that stream system.
>> Oh! That's so cool. I didn't know that.
>> Yeah, it's super cool. So, sometimes when they build their first dam, they start building up so much water . . . so much water gets built up behind it, it could damage the main dam. So, they'll build tiered dams, so that the water can cascade down and they still have this whole structure to live amongst.
>> They're like nature's engineers!
>> Oh, totally.
>> That's blowing my mind right now, that they're able to do that. So . . . the cool thing about these dams is that, obviously, they have so many benefits for the beaver themself.
[14:02.]
But, they have benefits to the ecosystem around them, right?
>> Oh, totally. We sometimes refer to them as, you know, "ecological engineers." Essentially, not only are they damming up the stream, which is for their protection, but then it's great for the streams themselves, you know? Many of our riparian areas these days haven't had beavers. They've had so much human influence that . . . they're so deeply cut that in some cases, when we see droughts, the streams are no longer connected. The flow of water is a lot faster than it probably should be. In many cases, when the water gets too channeled, too deep, it cuts into the ground. A lot of the riparian vegetation that other animals rely on dries up. It can't grow.
By building a dam, a beaver is slowing the flow of water in that area, and that can back up water, which can bring back riparian habitats. So, not only is that good for the plants to regrow . . . then it provides food, you know? Up north, moose really benefit a lot from beaver dams, because they rely on willow. Willow really needs slow moving water.
>> Oh! Okay, yeah.
>> And so, they build that habitat. Moose can take advantage of it, you know? A lot of fish species . . . there's some species that need slower moving water, and those dams can slow the flow of water and provide more habitat for fish. Many of our amphibians, frogs, salamanders, they can benefit from the slowed down water, or the pooled water. Then, it builds up a lot of nutrients in the water, and down the soil . . . so, it's just throughout pretty much every species out there, it can benefit. Even ducks, wood ducks especially really like to spend time in those beaver dam pools.
>> Who would have thought, beavers have this huge impact?
>> Yeah. They're really great for the environments that they're in. We're actually seeing in some cases; there's areas where we just don't have beavers. They haven't returned, because, you know . . . beavers used to be throughout pretty much all of North America.
[16:02.]
At least in the U.S., most of Canada, and parts of Mexico. Then, we just trapped them all out. You know, there was a drive for fur, beaver pelts in the 1800s.
>> Yeah, people want the fur.
>> The fur, yeah. And, their castor oil is very useful for many products, medicines, perfumes . . .
>> Hold up . . . the castor oil? Is that the oil that helps them stay water repellent? Or is that something in them . . .?
>> That's a good question. I'm not sure if they use the castor to waterproof their fur or not. That's another good question. I always get split if that's . . .
>> Sure.
>> It has a lot of uses, we'll just put it that way. So, we trapped them out, and there's all these riparian ecosystems that were used to having beavers help control the water. Without that, it really had issues. Long story short here, is that despite a lot of beaver populations recovering throughout the country, there's still areas that we don't have beavers yet. And the riparian areas still aren't in great shape. So, we're actually . . . there's people, and we're doing this in northwest Montana right now. We're putting in these, what we call, "beaver dam analogs." So, actually building . . .
>> Like, fake beaver dams?
>> Fake beaver dams. Driving wood posts in the ground, weaving timber and local vegetation in, to slow the water down. It builds up the sediment, and that has the same effect as a beaver dam. In some cases, we are seeing beavers finding these analogs and then setting up shop, because "hey, there's already a structure here, why don't I just maintain it?"
>> Ahh.
>> So . . . they're just being great. We're using them here in Missouri. I know out west, in the mountain west especially, because drought is a really big issue . . . everywhere it's an issue, but the mountain west really has issues. They are so dependent on slower-moving snowmelt water. Without beavers, it has impacts on a lot of the streams out there. So, they're using them a lot out there and having a lot of success, too.
>> That's incredible!
[18:00.]
Now, with putting these analog dams in there, did they know that that would happen? [unclear.]
>> Yeah. The hope was, if there were beavers in an area . . . the project we're doing in the northwest right now, the hope was to get beavers to come in and help maintain those dams. In some cases, get them to populate the area, to help build more natural dams in those areas, to revitalize the stream systems.
>> Ingenious!
>> Oh, yeah.
>> That's really, really great news for that area. So, does that kind of go along with them being a "keystone species"? You had told me about this previously, and I had never heard this term before. Explain that?
>> Yeah. I definitely think of them as a keystone species. If you think of the keystone in an arch, you have a stone arch, and at the very top is that forked stone that holds everything together. You take that out, and the whole arch falls apart. For sure, without having beavers in many ecosystems, you lose quality riparian areas, which then has less quality food resources for many wildlife species. Then, the changes in the flow of the stream impacts all of those species that rely on the waterway. So, having a single beaver in a stream system can really have cascading effects of providing habitat to a large tranche of wildlife species.
>> So, what's the state of the beavers in Missouri? Are they doing well?
>> Overall, they're doing very well. Once conservation efforts were put in place to limit trapping, we saw beavers naturally recolonize the Missouri river and spread out from the tributaries. I think much of the recovery of the beaver population was natural in this state, but I think there might have been a few places where they were brought back. Overall, they are doing really good, which is great. But that can lead to conflict, unfortunately. You know, as great as they are at building dams, and helping with stream systems, there's humans out there too, using those waterways. In some cases, it can cause issues. Anywhere from building dams across culverts, which then back up and they can flood agricultural landscapes . . . that obviously is an issue for our farmers.
[20:04.]
Some . . . the timber industry, you know, there are some places where there's quality timber growing along streams. Beavers are going up and chewing on the trees, and knocking them over, or even . . . you know, there's a lot more houses being developed near streams, and beavers are chewing down these beautiful trees build in neighborhoods.
>> Mhmm.
>> So, it becomes tricky. Because they're a really great species for the landscape. But as the human population expands, they are becoming issues. Unfortunately, there are cases where we do have to remove beavers from areas. It's definitely necessary, because if you leave them there, it's just going to cause a lot of issues. Especially for our agricultural producers, they put a lot of effort into producing all that food that we rely on. When you have beavers damming up areas and messing with the growth cycle, that's definitely something we have to take into consideration, and respond to appropriately.
>> It's a fine line to walk between sharing the landscape with humans, and wildlife.
>> Oh, totally! It's always . . . I think one of the most difficult things we have as a conservation agency. We have a lot of people that want to see the wildlife on the landscape. I think most people do. But there's always that line of, we have to find a way to coexist. The wildlife with us, and us with the wildlife. There's sometimes those lines that we have to respond . . . in some cases, it's removing animals from the landscape.
>> Do you have any final thoughts that you'd like the public to know about this species?
>> I think we've covered a lot of it. They're such an interesting species . . . everywhere from being the largest rodent species we have in North America, to the fact that they can build these dams that have such a huge, positive impact in most cases, to the local ecosystems . . . it's really great to have them. The positive effects we see in many cases on the landscape, it's really great to see. Like anything, like we just said, we always have to remember that it's always a balancing act. So, there's days that we just need to remove animals, and it's unfortunate.
[22:04.]
But, our population of beavers in the state is doing very well, and in most areas of the country. So, removing a few beavers here and there to help everyone be able to tolerate each other on the landscape is important.
[Music ♪.] [Water splashing sounds.]
>> Beavers need those strong and razor-sharp teeth to chew through trees. But why are they orange? It's iron! Iron in their enamel turns the teeth that orange or rust color. And it's what makes their teeth hard as steel for cutting. What I also found out, is that their lips close behind their teeth, which allows them to hold a branch with their teeth, while they swim under water, and not drown. What's also cool? They have an extra set of eyelids that's see-through and acts as swim goggles to protect their eyes when they're under water.
[Water splashing/nature sounds.]
As Nate was mentioning, beavers are native to Missouri's landscape, but conflict can occur between beavers and property owners. To learn more about mitigating conflict with beavers, visit our website or contact your local wildlife damage biologist. You can find resources and contact information on our website, at missouriconservation.org. Thanks again to furbearer biologist Nate Bowersock, to NatureBoost producer Peg Craft, and to you, for listening to another episode of NatureBoost. Be sure to check out next month's episode, where we'll be giving you a behind the scenes look or listen at Missouri's State Forest Nursery, and learning how its seedling sprouting operation has been helping restore our green spaces for over 90 years.
I'm Jill Pritchard with the Missouri Department of Conservation, encouraging you to get your daily dose of the outdoors!
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