Meet the Giant Beaver

Imagine traveling back in time to Minnesota at the end of the last Ice Age — 15,000 years ago. You would find Minnesota covered in dense wetlands, waterways, and lakes formed by receding glaciers. If you were to tread very quietly through this Ice Age landscape you may chance upon a remarkable rodent — the size of a small bear! You would not need to worry. This gentle giant is a herbivore, thought to munch on meals of aquatic plants.

The replica of the giant beaver at the Bell Museum sometimes seems to be (literally) overshadowed by its contemporary, the wooly mammoth – but the story of this giant member of the rodent family is just as fascinating a piece of Minnesota’s Ice Age History

Meet the Giant Beaver

The giant beaver, Castoroides ohioensis, was the largest rodent ever to have lived in North America, growing up to seven feet long and weighing up to 200 pounds. These enormous rodents roamed the wetlands and waterways of Minnesota until about 10,000 years ago. They shared the landscape with other megafauna, such as the woolly mammoth and giant bison.

Beyond their size, there are several significant differences between these Ice Age giants and the beavers we are familiar with today. The tail of the giant beaver was likely long and narrow, like the tail of a muskrat. Their front incisors were shaped differently than the incisors of modern beavers, lacking the chisel-like edge that made it possible for modern beavers to gnaw on woody vegetation. The lack of this feature suggests that giant beavers did not have the capability to build dams. Additionally, isotope analysis shows that woody vegetation was not a part of their diet.

Their inability to chew wood may have contributed to these rodents’ eventual extinction. Changes in climate likely led to a loss of habitat for the giant beaver as well as affecting their source of food. Unable to engineer their watery environment like modern beavers, the giant beaver may not have been able to keep up with the changing landscape. They became extinct around 10,000 years ago, vanishing alongside many of their megafauna contemporaries.

Remains of a juvenile giant beaver on display at the Science Museum of Minnesota. Photo: Alyssa Gregory

Humans and the Giant Beaver

Giant Beavers occupied the state’s Ice Age landscape at the same time as the first people arrived in what is now Minnesota. Although there is no conclusive evidence that humans hunted giant beavers, they almost certainly would have met. Human artifacts were discovered alongside giant beaver remains. Tales of giant beavers survive in oral histories of Native people of North America. 

Fossil Evidence 

The scientific name for the giant beaver, Castoroides ohioensis, was named after giant remains that were discovered in 1837 in Ohio. However, evidence of giant beavers reveals that their range extended throughout Canada and the United States. (A close relative, Castoroides dilophidus, lived in the Southeastern United States.) As the last Ice Age drew towards an end, the majority of Castorides ohioensis seemed to make their home in the region south of the Great Lakes.

Compared to other megafauna (such as the giant sloth, where only one has been found in Minnesota), discoveries of giant beaver remains have been relatively numerous throughout the state. In 1938, construction workers working for the Works Progress Administration made a fascinating discovery while building an access road to Hidden Falls when they stumbled upon the remains of a giant beaver. This specimen was likely a juvenile giant beaver who had scrambled into a limestone outcropping — perhaps seeking shelter — only to be crushed beneath collapsing rock. Its skeleton can be seen at the Science Museum of Minnesota.

A fairly complete skeleton was also found in North Minneapolis in the 1960s. In Wells, Minnesota, the distinctive incisor of a giant beaver was found while digging a well! 

Vote for the Giant Beaver!

Did you know, Minnesota is one of only 4 states not to have a fossil as an official state symbol? In late 2021, the Science Museum organized an online vote to let the people of Minnesota decide which fossil would represent the state. Originally there were eight candidates, ranging from fossilized bacteria to sharks. There was also an opportunity for voters to write in. That is how the giant beaver entered the competition. Although there were several write-ins, the giant beaver stood out and became the 9th candidate. 

Overall, 11,500 votes were cast, with the giant beaver as the clear winner. It was then time to make it official, starting with the legislative session in 2022. Unfortunately, the state fossil was included in an omnibus bill, which ultimately did not pass. The bill did not pass in 2023 or 2024 either, despite a statewide educational campaign – from a Beaver game in Bemidji to Beaver Brewery in St. Cloud – and countless school classrooms in between. 

Alex Hastings, paleontology curator at the Science Museum, weighed in on the nearly 5-year long endeavor. According to Dr. Hastings, the educational potential makes it worth the effort. Dr Hastings explained that, whereas almost everyone can name Minnesota’s state bird, it is a challenge to let people know that there are even fossils in Minnesota. This is a chance to engage the people of Minnesota with the state’s prehistoric past! Beyond paleontology, bringing the campaign for the state fossil to classrooms teaches kids about civics and the process of introducing new bills. 

The giant beaver is connected to the Ice Age past of our region. The species made its home in what is now Minnesota, when the landscape and waterways were being shaped and reshaped by shifting and melting glaciers. It inhabited the land at the same time as people arrived in the state and left its legacy throughout the Great Lakes region in the form of fossil evidence. 

Would you like to see the giant beaver as the state fossil? The best way to help is to contact your State representative! 

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