Beavers might not be the cuddliest animals, but they’re not monsters… are they? At least they’re not monsters anymore. Tens of thousands of years ago, enormous beavers approximately the size of humans roamed the earth. Before we could interact with them, though, this impressive species went extinct, leaving modern-day scientists with fossils, theories, and lots of questions.

Were these enormous beavers the same as today’s beavers?

Although scientists know enough about these gigantic mammals to call them beavers, they weren’t exactly identical to the tail-slapping dam-building animals we know and love today. Ancient enormous beavers probably didn’t have the same type of tail: the beaver tails of yesteryear probably resembled a long and skinny muskrat tail more than the paddle-shaped beaver tail we’re familiar with now. Although the rest of the ancient beaver body would be recognizable as a beaver today, ancient beavers also had different teeth. While their teeth weren’t as sharp as modern-day beavers’ teeth, they were bigger, bulkier, and curved, suggesting a slightly different diet.

While people have known about these prehistoric beasts for centuries, many elements of their lives were still unclear until recently. Mammoth beavers were big and prolific, appearing everywhere from Florida to the Yukon and weighing up to 100 kilograms. But now, thanks to modern technology, we know much more about these massive animals than just what they looked like.

Why did the big beavers die out?

Mammoth beavers went extinct at the same time as a lot of other ancient animals, like the woolly mammoth. However, it wasn’t until recently that scientists could pinpoint an exact cause of death. To delve deeper into the life and death of these enormous mammals, scientists undertook an exploratory trek into the ancient bones of the beavers. Using modern research and technology, researchers were able to delve into the fossilized bones to find stable isotopes, chemical markings from the diet of the long-dead animals. This incredibly preserved chemical information tells us what the beavers ate, allowing scientists to make predictions and formulate theories about how they lived and why they died.

The information provided by the stable isotopes in beaver bones was astounding. These big beavers may have looked strikingly similar to our beavers today, but their lives and favorite foods were anything but. Instead of whittling down trees and ingesting woody plant matter, ancient beavers subsisted on aquatic plant life. Not only does this discovery give rise to extinction theories, but it also changes scientists’ understandings of the role the beavers played in their ancient ecosystems and environments.

Knowing that gigantic beavers ate aquatic plants gives scientists a major insight into the animal’s eventual downfall. Because they relied on aquatic plants, they were overwhelmingly affected by climate change. Around 10,000 years ago, the planet started to warm up, causing the mammoth beavers to lose their homes and their food sources when their familiar wetlands evaporated. As the warming continued, modern beavers took the stage. The lives of mammoth beavers and modern beavers overlapped a little bit, but because of the modern beaver’s ability to create its own living space and survive off of different types of plant matter, it outlived its enormous cousins.

Why do we care about mammoth beavers today?

Although mammoth beavers aren’t poised to rise from the depths of the bog and attack our rowboats, there is still valuable information to be gained from studying them, their lives, and the causes of their extinction. As we learn more about the impacts of climate change of different species of plants and animals, we can work to preserve our world for generations to come. Studying the life and death of the mammoth beaver isn’t just interesting, it may be life-sustaining.