The world's largest living rat can weigh up to half a ton.

The capybara (Hydrochoerus hydrochaeris) is an unusually large rodent. In fact, it is the largest living rodent in the world – despite being a rat, it is the size of a Labrador dog.

Capybaras are found throughout much of South America and live in forests next to water. They love being in the water and spend most of their time swimming, avoiding jaguars and eating a lot of grass.

Capybaras can weigh between 35 and 66kg and can grow up to 1.3 metres in length. Females are usually larger and heavier than males. They are 60cm tall. They are about the same size as Labradors, although they are stockier and heavier.

These rats are closely related to guinea pigs and cave rats. However, they are not the largest rodents that have ever lived – Josephoartigasia monesi looked similar to a capybara but lived 2 to 4 million years ago. These monsters weighed a ton, and were 3 meters long!

The ancient Josephoartigasia monesi had a short neck and a stout body, filled with fatty tissue. They walked and ran on all fours like modern bison. Like capybaras, they had four toes on their front feet and three toes on their hind feet, connected by a webbing that allowed them to swim. Unlike most modern rodents that have long tails, they were either tailless or had tails that were much shorter in proportion to their body size.

The scientific name of the capybara comes from Greek and roughly translates to 'water pig' (both the genus and species name). Although they are not pigs, these rats love water.

They are semi-aquatic mammals and spend much of their time in water. They live most of their lives in dense forests next to lakes, rivers or swamps.

Capybaras have special adaptations for their life around wetlands. They have slightly webbed feet that help them swim. They can also press their ears against their heads to keep water out and can stay underwater for up to 5 minutes. This behavior may help them hide from predators.

Their eyes, ears, and nostrils are all located on top of their heads, allowing them to keep most of their heads submerged in water. This also makes them less visible to predators, but still able to see what's going on.

These giant rats even mate underwater .

Today, the world's largest rodent is the capybara , which lives in Paraguay, Argentina, Brazil, Bolivia, Colombia, Venezuela and most of northern South America. Compared to other rodents, their size is still very large with a body length of 1.3 meters, a shoulder height of 0.5 meters and a weight of 35 to 66 kg.

Capybaras are picky eaters and will only eat very specific plants. However, they will eat a wider variety of plants during the dry season when their preferred species are not available.

These giant rodents feed primarily on grass and aquatic plants. They also eat their own feces to maximize nutrients and aid digestion by accumulating beneficial bacteria.

'It's called coprophagy —a mechanism to take in all the nutrients,' Elizabeth Congdon, a professor and capybara researcher at Bethune-Cookman University in Florida, told  The Verge .

Like other rodents, their teeth are constantly growing due to constant wear and tear from eating.

They eat 3-4 kg (about the weight of an average cat) of grass per day. Capybaras chew from side to side (like camels), while humans chew up and down.

True to its name, capybaras are particularly fond of water. They even mate while underwater. Capybaras can dive and stay underwater for up to five minutes. According to National Geographic, they are "excellent swimmers ." Their webbed feet help capybaras move easily through water. Their semi-aquatic lifestyle also helps them escape from being chased by wild cats, eagles, and anacondas.

Under ideal conditions, capybaras can live up to 10 years, but they usually do not live longer than 4 years in the wild because they are often considered a tasty meal for jaguars, cougars, eagles, caimans, and anacondas.

These rats are social and usually live in groups of 10-20, although during the dry season they can live in groups of 40 or more.

On land, this species also possesses impressive speed. It can accelerate up to 35 km/h - equal to a horse.

The behavior of these animals is often compared to that of cows — they just need to be left alone and have grass to eat.

However, capybaras seem to be quite easy to train : they are sometimes kept as pets, and one blind man in Suriname used one as a guide animal. Owners of the giant rats also say they learn simple tasks faster than dogs.

Capybaras are also kept as pets. In Japan, a zoo called Izu Shaboten even bathes them in hot springs to attract visitors.