We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is the Largest Rodent That Ever Lived?

Michael Anissimov
Updated May 21, 2024
Our promise to you
All The Science is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At All The Science, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

The largest rodent that ever lived was the size of a cow. It was 3m (9.8 ft) long, with a 1.5 m (5 ft.) tail, and probably weighed around 700 kg (1,543 lbs). This rodent could kill you if it sat on you.

Actually, the figures cited are for Phoberomys pattersoni, which is only the second-largest rodent that ever lived. Its close cousin, Phoberomys insolita, was even a bit larger, but no complete skeleton of it has ever been found, making a precise estimate of its size and weight difficult.

Phoberomys pattersoni lived in the Late Miocene, about 8 million years ago. It dwelled around the Orinoco river delta in modern-day Venezuela, feeding on grasses and shrubs. Its sheer size would have been a deterrent to predators, much like its herbivore contemporaries, the ground sloths.

Like other rodents, Phoberomys pattersoni had large, continuously growing teeth that had to be kept short by gnawing. These teeth, the size of sabers, would have also been used to bite would-be predators. It is not likely that Phoberomys pattersoni had any serious predators, because being so large, it was likely relatively slow, and would have been easy prey for the mega-predators of the time if it couldn't defend itself in a fight. The fact that it even evolved suggests that it could.

Phoberomys pattersoni's natural predators would have included three-meter long crocodiles, saber-tooth cats and huge, flightless carnivorous birds. Living a semi-aquatic lifestyle, it probably ate sea grass.

A full skeleton of the beast was only discovered in 2003. Fragments had been uncovered before, but no one suspected how big the rodent was until the full skeleton was found. Its closest living relative, the South American capybara, can weigh up to 45 kg (99 pounds), 15 times smaller than Phoberomys pattersoni. The capybara is the largest living rodent.

Phoberomys pattersoni managed its huge size by using a different gait than smaller rodents. Its massive stomach would have aided its digestion by functioning as a fermentation barrel to break down stubborn bits of cellulose.

All The Science is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Michael Anissimov
By Michael Anissimov
Michael Anissimov is a dedicated All The Science contributor and brings his expertise in paleontology, physics, biology, astronomy, chemistry, and futurism to his articles. An avid blogger, Michael is deeply passionate about stem cell research, regenerative medicine, and life extension therapies. His professional experience includes work with the Methuselah Foundation, Singularity Institute for Artificial Intelligence, and Lifeboat Foundation, further showcasing his commitment to scientific advancement.
Discussion Comments
By Ana1234 — On Aug 10, 2014

@umbra21 - Hippos are vegetarians but there is plenty of reason to fear those. They are one of the worst killers of humans among all the big animals in Africa.

These giant rodents sound like they are fairly similar, being semi-aquatic and living on sea grass. So they might have been sweet and gentle like manatees are today, or they might have been like hippos. And since hippos are that violent to deal with the predators they face, I would imagine that a cow-sized water-rat would be fairly violent as well, considering it was dealing with massive crocodiles and saber-toothed cats.

By umbra21 — On Aug 10, 2014

@irontoenail - Rats and mice have a reputation (and not undeserved) for being dirty as well as being vicious and that might be why some people are afraid of them. They forget that squirrels are rodents as well, and so are guinea pigs, but fewer people are afraid of those.

The difference is that rats are omnivorous. There are plenty of stories about rats taking a bite out of people or animals or even devouring them alive when they have the chance. It sounds like this creature was massive, but not carnivorous so there wouldn't be any reason for a human to fear it.

By irontoenail — On Aug 09, 2014

I guess if you have a problem with rodents you probably wouldn't even recognize this creature as being a rodent. My mother is terrified of mice and rats (although she always just says she strongly dislikes them) and will literally jump onto a chair if she thinks one is in the room.

But I suspect that's because they are small and unpredictable rather than because they are actually all that dangerous.

Michael Anissimov
Michael Anissimov
Michael Anissimov is a dedicated All The Science contributor and brings his expertise in paleontology, physics, biology...
Learn more
All The Science, in your inbox

Our latest articles, guides, and more, delivered daily.

All The Science, in your inbox

Our latest articles, guides, and more, delivered daily.