How Big Is a Capybara? The World's Largest Rodent

Capybara size at a glance

The capybara is built like a barrel on short legs. Most of its length is body: the head is broad and blunt and the tail is only a tiny stub, so almost all of that 1.1–1.3 m (3.5–4.4 ft) is nose and torso.

In one well-studied population in the Llanos of Venezuela, adults averaged about 49 kg (108 lb). Figures in the 50–60 kg (110–130 lb) range are often given as a typical average, and weights vary between regions and with the season, since capybaras lose condition in a hard dry season.

Are female capybaras bigger than males?

Yes, slightly. Female capybaras are on average a little heavier than males, which is unusual among large mammals, where males are more often the bigger sex. The difference is small, and in the field the sexes are easier to tell apart by the male’s morrillo, a large, bare, dark scent gland on top of the snout.

How fast do capybaras grow?

Capybaras grow quickly. Pups are born after a pregnancy of about 130–150 days, weigh only about 1–1.5 kg (2–3 lb) and already have fur and open eyes. They start grazing within a week and are weaned at about three to four months, by which time they are many times their birth weight.

Young capybaras stay small and vulnerable for much of their first year, which is why so many are taken by caimans, eagles and other predators. They reach breeding age at around 15–18 months, close to full adult size. Because most wild capybaras live only about 4–6 years, adults spend most of their lives at or near their full size.

Record weights

The heaviest wild capybaras on record are a female from Brazil of about 91 kg (201 lb) and a male from Uruguay of 73.5 kg (162 lb). An individual of around 81 kg (179 lb) has also been reported from São Paulo state in Brazil. These are exceptional animals; a capybara over 70 kg (154 lb) is very large.

How does a capybara compare with other rodents?

There are more than 2,000 species of rodents, and most are small: a house mouse weighs about 20 g (under 1 oz) and a brown rat about 250–500 g (9–18 oz). The capybara is in a different league.

Beavers are the largest rodents in North America and Europe and are usually ranked just behind the two capybaras. A typical adult North American beaver weighs around 20 kg (44 lb), so an average capybara is roughly two to three times heavier. Very old beavers occasionally top 40 kg (88 lb), but that is still less than most adult capybaras.

The capybara’s closest living relatives are the guinea pigs and the rock cavies of South America. A capybara can weigh around 50 times as much as a domestic guinea pig, even though the two belong to the same family, Caviidae.

Extinct giant rodents

The capybara is the largest rodent alive today, but it is far from the largest that ever lived. South America was once home to true giants.

Josephoartigasia monesi, known from a skull about 53 cm (21 in) long found in Uruguay and dated to a few million years ago, is the largest rodent known. Because only the skull has been found, its weight is hard to estimate. Published figures range from about 500 kg (1,100 lb) to around 1,000 kg (2,200 lb) or more, about the size of a bull. It was related to the pacarana, not to capybaras.

Phoberomys, from the late Miocene of Venezuela and neighboring countries, was another giant, with weight estimates ranging from about 125 kg (276 lb) to several hundred kilograms. Among true capybara relatives, Ice Age capybaras such as Neochoerus lived as far north as the southern United States, including Florida, and some of them are thought to have been larger than the living species.

Why are capybaras so big?

Large size helps a grazing animal. A big gut can hold more grass and give bacteria more time to break down tough plant fiber, which is why most large grazers, from cattle to hippos, are heavy animals. Size also protects adult capybaras from smaller predators such as ocelots and eagles that readily take young ones; only jaguars, pumas and large caimans and anacondas regularly kill adults.

Living in water helps too. A capybara’s body is only slightly denser than water, so it floats easily, and wallowing keeps such a large, heavy animal cool in the tropical heat.