Capybara: the charming, largest rodent living in South America

Our “Species of the Week” series highlights the flagship species of each of the 844 unique ecoregions contained within Earth’s bioregions.

Ever seen a beaver and thought, “gosh, that’s big?” Then you’ve probably never seen a capybara. At almost twice the size, the capybara is the largest rodent on Earth. Closely related to guinea pigs and rock cavies, they’re distantly related to chinchillas and agouti, and, although decidedly cuter, strongly resemble the ROUT - that is, the Rodent of Unusual Size from the movie “A Princess Bride.” Those were fictitious, but the capybara couldn’t be more real. 

Semi-aquatic mammals with an average weight of around 110 pounds, female capybaras tend to be a little heavier than their male counterparts. They’re native to South America and they make their home near bodies of water, such as lakes, rivers, swamps, ponds, and marshes, in densely forested areas. Strong swimmers, they can hold their breath underwater for up to five minutes at a time.

Their barrel-shaped bodies are covered in reddish-brown brittle fur that dries out quickly on land. When swimming around with the help of their webbed toes, they’re able to survey their above-water surroundings, thanks to small eyes, noses, and hairless ears located high on their heads. They have a lot to watch out for, as they happen to make a favorite meal for a variety of predators including jaguars and pumas on land, and, in the water, caimans — a crocodilian alligatorid. Meanwhile, their young are a much sought-after treat for anacondas and other snakes, forest foxes, small cats, and birds of prey like the harpy eagle, caracara, and black vulture.

Unlike the ROUT, capybaras are vegetarians, gnawing primarily on grasses and aquatic plants, and since they chew food by grinding back-and-forth, their front teeth grow continuously to compensate for constant wear. They’re also autocoprophagous, which is a fancy way of saying they eat their own feces. This provides them with a source of bacterial gut flora, and since animals can't digest grass very well on the first try, eating it twice helps them get all the nutrients they need.

If that bit of information doesn’t land them on your “cute” list, consider this: capybaras are super chatty, and love to sing little songs. Highly social mammals, they live in groups of usually 10 - 20, and express themselves by purring, barking, whistling, squealing, cackling, whining, grunting, and even teeth-chattering. Each sound a capybara makes bears a significant meaning, from alerting the group to danger, to showing approval, to signaling departure or arrival. When a group of capybaras decides to go on the move, they form a chirping chorus that could give a flock of songbirds a run for its money.