There's more to capybaras — those bizarre-looking rodents that are slowly taking over the internet by soaking in hot tubs and cuddling with humans — than meets the eye.

Read on for some fascinating facts about these adorable animals.

1. They're Basically Giant Guinea Pigs

Capybaras are related to rock cavies and guinea pigs. Charlesjsharp [CC by 4.0]/Wikimedia Commons

Standing 1.5 feet tall at the shoulder and weighing in at up to 150 pounds, capybaras are the largest rodents in the world. In fact, they're closely related to guinea pigs and rock cavies and distantly related to agoutis and chinchillas.

2. They're Semiaquatic

Capybaras have webbed feet, which makes them great swimmers. Tambako the Jaguar [CC by 2.0]/flickr

Native to Central America and northern South America, capybaras spend most of their time lounging in or near lakes, ponds and rivers and eating 6 to 8 pounds of grass and aquatic plants a day.

They have webbed feet, making them great swimmers, and their eyes, ears and nostrils are located at the top of their heads, enabling them to keep most of their bodies below water like hippos. Capybaras can also press their ears against their heads to keep water out, and they can completely submerge themselves for up to five minutes, allowing them to hide from predators like jaguars, pumas and ocelots.

And just in case you thought we were kidding about the capybaras enjoying hot springs, here's proof!

Capybaras coming for a soak at onsens has become something of a tradition in Japan over the past 30 years or so. Some especially lucky capybaras get treated to the customary New Year's inclusion of citrus in the water, so they're able to leave the spa with that fresh, clean lemon scent!

3. Their Teeth Never Stop Growing

Capybaras chew on bark to help wear down their front teeth (Tambako the Jaguar [CC by 2.0]/flickr)

Capybaras have two long front teeth, and like other rodents, these teeth must be worn down by chewing on food or bark.

4. They're Kept as Pets

Capybara Caplin Rous swims with his owner, Melanie Typaldos. Barcroft/Getty Images

Capybaras are wild animals that aren't accustomed to living in homes, but that hasn't stopped people from keeping them as pets. The creatures require a great deal of outdoor space for grazing, as well as a body of water for swimming, and feeding them can be expensive.

The most famous pet capybara is probably Caplin Rous (Rous stands for "Rodent of Unusual Size," for all you "Princess Bride" fans), and he lived with the Typaldos family in their Texas home. He's pictured above swimming with owner Melanie Typaldos.

5. They're a Great Place to Sit

A bird perches on a capybara's head. Mohit Yadav [CC by 2.0]/flickr

Sometimes referred to as "nature's ottoman" or "living chairs," capybaras have developed a reputation as being a nice place to take a load off.

Birds, monkeys, rabbits and even other capybaras have been photographed perching, sitting and lounging atop these large rodents, and there's even an entire blog devoted to these adorably amusing pictures.