Capybaras are the world’s largest living rodents. Extinct species of capybaras are even bigger. So when people claim to have seen a capybara on a river bank in [Idaho, Missouri, Oregon] they have seen a nutria, which is maybe about twenty pounds. Muskrats are about four pounds. Beavers can weigh up to sixty pounds, but if you see that tail, there is no mistaking a beaver. Full grown capybaras weigh about one hundred and forty pounds. That is one big motor scooter.
So many of the cute, friendly capybaras you see online are babies. At birth, they are about the size of a muskrat. A couple months later, they are already the size of a nutria. Around a year they have grown to the size of a beaver.
It takes a couple years to attain their mature size, and by then most people have figured out that this is not a cute, chill animal, but a major handful, best turned outdoors for the duration.
- Three weeks
- About three months
- Seven months
That is not to say big is bad. But during their formative years, when they are still adorable and relatively docile, you darned well better devote your time to training, taming, and accommodating your little monster.
Because they are so intelligent, the range of personalities is infinite. Some remain cuddly, some stay forever skittish, some are simply suspicious and mean-tempered. It’s a crap shoot, and if you get one that is stand-offish, you had best devote some serious training time while they are smaller than you.
- At three weeks, he lived in a big bathtub with an eggo box for a shack.
- At ten months he had moved to the big bathtub for swimming.
They grow quickly. Dobby outgrew a regular bathtub before he was a year old. Capybara bathing is the only conceivable use for this Jacuzzi tub. I’m joking, of course. I have used this tub to rehabilitate ducks and hens post-surgery, and of course Princess the hen slept on the edge for three years. But I digress.
- At three weeks, he was smaller than a duck.
- At eight months, Dobby easily fit under the dining table where he stealthily ate our shoelaces
- At eleven months, he respected the 24″ tall x-pen that kept him out of the dining room.
It wasn’t Dobby’s size that caused him to be banished from the house. Sure, he still had access to the kitchen, but he insisted upon marking his territory. Trust me, you do not want a capybara to mark your bedroom. Or anywhere in the house. But size is a problem if you need to sequester him.
- Table height, standing
- Bigger than a garbage can
- Counter height, standing
I installed linoleum over my wood floors and set solid-core doors on side to create a pen. To be honest, he could have jumped these walls but he understood that he had been given his own territory. He never missed an opportunity to survey the house if the door was left open, though.
- 5 gallon bucket for scale
- Doorknob height for scale
- Garbage can, compare to teeth for scale
- RR track for scale
I cringe when I hear people claim they want a capybara because “they’re so cute.” The babies are cute, the adults are formidable. Someone contacted me recently about bringing my capybara to a birthday party. For a one year old child. That is what prompted me to write about size. People have no clue.

Mona Lisa, shown here with a 3 to 4 month old capybara. A full-grown capybara could have sat up and looked her in the eye. Might have had to redo her facial expression.
In my opinion, even grownup capybaras are cute. Dobby stayed adorable throughout his 9.5 years of life. Beauty is in the eye of the beholder, though. An uninformed person might well be intimidated by a mature capybara. Young capybaras become rambunctious teenagers and fairly destructive adults. If you now understand this, my work today is done.
- About 7 months, indoors
- About two years, with his own outdoor bathtub and spa
Destruction demo follows:
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