Because the beaver isn't just an animal; it's an ecosystem!

Category: castoroides


Sometimes in order to get folks to really pay attention you have to talk like a scientist. Good thing for beavers Zane Eddy’s thesis defense is now available online to tell the story of the Martinez Beavers from an academic’s point of view. This is so well done with lots of explanation on the expanding nature of “Cultural Carrying Capacity” and even has video from the actual November 7th meeting I hope you’ll watch and share.

Thank you Zane for all your hard work and congratulations!

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Afterwards if you have change burning a hole in your pocket this morning I know just what you should spend it on, as a very rare castoroides skull is up for auction at Bonham’s today.  Thanks Rickipedia for the tip. I can imagine him with something like this on his wall. How about you, are you tempted?

Giant Beaver Skull

US$ 25,000 – 30,000
£ 18,000 – 21,000Natural History

25 May 2021, 10:00 PDT

Los Angeles

Castoroides ohioensis
Pleistocene
Florida

One of the main anatomical differences between the Giant Beaver and modern beaver species, besides its massive size, is tooth structure. Modern beavers have chisel-like incisor teeth for gnawing on wood. The teeth of the Giant Beaver were bigger and broader, growing to about six 3 inches in length. Also, proportionate to its size, the tail of the Giant Beaver was longer and narrower, and its hind legs shorter. The first Giant Beaver fossils were discovered in 1837 in a peat bog in Ohio, hence the species name ohioensis. The present specimen displays excellent preservation and expert preparation. The upper incisors are original. Specimens of this size and quality are very rare. Offered on a custom base. Measuring 14 x 11 x 9 in

Now I can remember when I thought I was insane for buying the copy for 350 way back in 2008. It just struck me as hilarious to show up at a city council meeting with this on my lap. But the real thing would have been wayyyy more funny.


The castoides skull copy is one our most prized beaver exhibit items. For years we’ve been answering questions about this dinosaur beaver, reporting the slightly incredible research based on isotope analysis that they didn’t eat trees but survived on very small pond weed. People always scoff at that, and say then what are those big teeth for? Which I can never explain.

But Castorides wasn’t the only beaver.

The family of castorids used to contain many members all evolved into their own niche and constrictions. Dipoides was actually smaller than our beaver and some brand new research indicates it miraculously cut trees for food. Wait, what? A beaver the size of a bear lived on pondweed and a beaver the size of a lapdog cut down trees? Well yes. Little trees. Do not ask me why on earth the giant beaver didn’t cut trees and the small beaver did. But that’s evolution for you, Apparently they cut the trees first, because they were hungry, and then when things started freezing their cousins thought, hey maybe there’s a value in building up the water and saving some unfrozen food.

Maybe being the midsized beaver that could do it all made sense in the long run.

Ancient Arctic beavers were cutting down trees for food at least four million years ago – long before they started building dams, study shows

By studying the wood-cutting behaviour of ancient beavers that once roamed the Canadian high Arctic, an international team of scientists has discovered that tree predation – feeding on trees and harvesting wood – evolved in these now-extinct rodents long before dam-building.

This is an important discovery as woodcutting is a key behaviour for modern-day beavers’ capacity to modify, create and maintain habitats.

This new research suggests that tree predation has existed for more than 20 million years, enough time that might have allowed beavers to affect the evolution of certain trees species.

The ancient beavers, belonging to the fossil lineage Dipoides, lived four million years ago and were approximately two-thirds the size of today’s Canadian beavers. They gnawed trees with rounded front teeth, not squared teeth like their modern relatives, and researchers believe this woodcutting behaviour originated for harvesting food, not from a compulsion for building dams.

The study, published today in Scientific Reports, is first-authored by Tessa Plint, a former Western University graduate student currently pursuing a PhD at Heriot-Watt University (UK).

“Ancient animals and ecosystems that thrived in the high Arctic during warmer times in geological history show us a glimpse of what this biome could look like in the future under the effects of global warming in polar regions,” said Plint.

“Today, the beaver has a profound impact on the landscape and is known to increase the biodiversity of the local ecosystem through tree-harvesting and dam building. It’s fascinating to look back in time and figure out how this hyper-specialized toolkit of behaviours came to be.”

At Western’s Laboratory for Stable Isotope Science, researchers examined chemical signatures preserved in ancient beaver bones to figure out what exactly they were eating four million years ago –and, surprisingly to them, it included trees.

So there you have it. Sometimes it looks like you’re suited for one purpose and it turns out you do something completely different and blow them all away. And sometimes you have the perfect seeming qualities, and everyone treats you as a “RINGER” for sure, and you fizzle out and eat pond weed.

Go Figure.


Winter tends to be a good time to think nice things about beavers, especially once the rain turns to snow and things are too frozen to cause a problem for a while. I really enjoyed reading this appreciative column from master naturalist Shannon Brennan in Virginia.

For Love of Nature: Beavers busy sculpting along James River

On a recent warm winter’s day, Michael and I headed for our favorite local trail at Matt’s Creek, across the James River Foot Bridge on U.S. 501. We were soon greeted by an amazing wooden sculpture, with shavings all around the base of a tree that would soon topple to the ground.

Other trees had already been felled, telltale signs that beavers had been busily gnawing along the banks of the James River, both to eat the bark and potentially use the tree for a dam, though there was no sign of a dam or lodge in the vicinity.

Beavers munch on small saplings and very large trees, leaving many people to decry the damage, but the damage humans inflict on trees pales in comparison. I prefer to call it beaver art.

We couldn’t agree more Shannon! In fact there are two beaver chews by my hearthside right now! I personally know several people who collect and take photos of them. The one I shared yesterday still happens to be my favorite.

While it’s true that damming creeks in urban areas, like Blackwater Creek, can interfere with water and sewer lines and exacerbate flooding, beavers are important parts of natural ecosystems.

Early residents of this continent considered beavers sacred because they create wetlands, the key to life for many species. Almost half of endangered and threatened species in North America rely upon wetlands, which also soak up floodwaters, alleviate droughts and floods, lessen erosion, raise the water table and purify water.

Although I’ve seen signs of beavers for years, I’ve yet to spot one. They are largely nocturnal and stealthy.

 I wish you had come to Martinez a decade ago and been able to watch entire families gathered together on the bridge to watch our beavers working and playing with each other. You would have been so happy.

Beavers rarely overpopulate because they breed only once a year and defend large streamside territories from other beavers. Trapping beavers often fails because removal stimulates larger litters among those left behind.

For me, it’s always a thrill to see where beavers have been busily chomping or sliding into a creek or river. I don’t have to see the animals to know that they are alive and well and doing their sacred duty.

I’m with you, Shannon. i think beaver sign is a wonderful secret handshake that tells people in the know that something dramatic is going right with that creek or waterway. Thank you so much for being happy about beavers. It doesn’t happen very often but it’s always a wonderful thing to behold.

Speaking of friendly words about beavers. since October I’ve been keeping a spreadsheet of the folks who contact me thru the website to ask about their beavers or how to save/introduce/or advocate for them. I’m always surprised how far afield these contacts come from, and I thought you’d be interested in the visual.

Not bad visibility for three months.


I know you read this website every day, but you’re probably thinking, wait, there aren’t enough folktales or origin myths about beavers being the beginning of everything. Heidi should write about the big stories once in a while. And I agree! So we’re grateful Frances Backhouse shared this.

The Hero of the Dene

Long ago, giant beasts roamed the Earth and people were lawless, and the Dene of the Northwest Territories tell of two brothers who set the world straight. “Many old medicine stories talk about giant animals—bats, dinosaurs, beavers, monkeys—which once roamed the earth,” wrote the late Dene elder George Blondin in his book Yamoria: The Lawmaker. “Storytellers say we came from animals and long ago there were many half-animal/half-human life forms. It seems during this period that genetic forces as we know them today were out of control.” People were starving and ate each other, he writes of this “terrible period.” But Yamoria and Yamozha came from the west to be humankind’s salvation.

People were lawless? Well, that I believe. How do beavers come into the story?

“My grandfather says, as the story goes, that people were really, really scared when they paddled, because at any time they could encounter a beaver,” says Sangris. “And beavers, they don’t have any natural enemies. They’d come to anything that’s moving on water and if they feel threatened and if they don’t feel comfortable, they’ll capsize the canoes and break the canoes. So the Dene here, the Yellowknives Dene were afraid of them. They were afraid of the beavers so they’d paddle right on the shoreline as quietly as they could go. And they would tell the children not to make any noise.”

Shhhh watch out for beavers!

Sangris says no one knows what happened to them after the fight, but perhaps where they ended up is not as important as the legacy they left behind. “It’s always said that Atachuukaii corrected things. He made things better,” Elle says. For ridding the world of giant animals, Sangris says the two brothers are heroes to the Dene. “The Dene were free after that. There were no giant beavers swimming around anymore and no big birds flew in the sky and no big animals walked on the earth that could harm them anymore.”

Well, I might be scared of a 300 lb beaver too.

Giant beavers (Castoroides ohioensis), the key antagonists in many Yamoria legends, actually existed in the swamps and lakes of the North around the time humans first arrived, between 40,000 and 16,000 years ago. And like the legends say, they may not have been all that easy to deal with.

The North of that time was host to a wide diversity of large mammals, including horses, camels and woolly mammoths. But around the end of the last glacial period, about 12,000 years ago, the giant species began disappearing.

But were the giant beavers hunted? Were they around the same time as the humans?

Theories of over-hunting by humans would back up stories of Yamoria shrinking or killing off many of the giant mammals that threatened humans at the time, but Grant Zazula, a paleontologist with the Yukon government, has his doubts, saying there’s little evidence of over hunting and no evidence that humans preyed on giant beavers at all. 

“A beaver the size of a bear with eight-inch teeth. I don’t know. If I was a hunter back then I would probably go with the horse or a bison.”

So how did giant beavers make their way into Dene stories? Zazula’s theory came to him the first time he did field work in Old Crow, in Northern Yukon.“If you go along the Old Crow River in the summer, and you float down in a canoe, there’s piles of bones of ice age animals on the riverbanks. They’re just all over the place.” 

So the beavers themselves might not have been around, but their bones were. Native saw those bones and came up with some pretty exciting stories to keep their grandchildren warm at night.

I remember the first time I saw a castorides skull my eyes grew bright, I immediately conjured a fantasy of sitting at a city council meeting with that giant head in my lap.

Wouldn’t that be awesome?

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