Average 100 pounds. The largest is about 175 pounds. They are about two feet tall and four feet long. Some books give a smaller weight for the largest capybara, about 140 pounds. I have one source that I consider reliable that says 175, and what’s more, I work with someone who met a 175 pound capybara. However, this is not common.

There were prehistoric capybaras, now extinct, that weighed about eight times as much.

Rodents have sharp front teeth that never stop growing. (Capybaras have a total of 20 teeth, including two pairs of typical rodent incisors and four molars on each side of the lower jaw.) Rodents must chew on things to keep their teeth from growing too long. Capybaras spend a lot of time chewing tough grasses.

There are more species of rodents than any other order of mammals: over 1,800 species.

Rats, squirrels and mice are other familiar rodents. (Rabbits and bats are NOT rodents.)

But capybaras are more closely related to guinea pigs, chinchillas, maras and other cavies.

Most rodents are much smaller than capybaras. The second largest rodent is the mara or Patagonian cavy. Maras are about a foot tall and weigh about 25 pounds. They differ from capybaras in that they are adapted for living for living in dry grasslands, so their bodies resemble those of small deer.

Capybaras are semi-aquatic, which means they spend a lot of time in the water.

They live in grasslands and forests alongside water, such as rivers and lakes, in the extreme south of Central American and the north of South America: Panama, Venezuela, Brazil, Colombia, Bolivia, Guyana, Suriname, French Guiana, and parts of Ecuador, Peru, Argentina and Paraguay. Many live in the Pantanal in Brazil and the Llanos in Columbis, which are large grasslands that flood for part of the year.

Capybaras are normally crepuscular, which means that they are active at twilight: early in the morning and at sunset.

They rest during the heat of the day, often in the water.

Where they are hunted a lot by humans, they may be nocturnal.

Their feet are webbed for swimming. This also helps them to walk on soggy ground. (If you watch how they walk you will see that they often seem to step like they are placing their feet very carefully, to test how soft the ground is.)

Their heads: their eyes, ears and noses are high up on their heads so they can see and breathe while swimming. If you watch them swim you can also see that they press their outer ears against their heads, closing their ears.

They can stay underwater for five minutes.

The scientific name for capybaras is Hydrochaerus hydrochaeris. It means 'water pig.' (When it was first discovered, people didn't know it was a rodent.)

(There is some inconsistency in the spelling of the scientific name. Here I follow Walker’s Mammals; see elsewhere on the website for discussion.)

When they are fully grown adults, their hair is coarse and spread fairly sparsely over their skin. This means that much of their skin is bare and they sunburn easily. They go into the water or rest in shade to avoid sunburn. They also sometimes dig wallows in the mud. They may roll around in the mud (like pigs) to protect their skin and keep cool.

Capybaras tend to dive into the water to hide from predators. They also prefer to defecate in the water.

Male capybaras have a scent gland on their nose that they use to mark their territory.

They make lots of different sounds like whistles, grunts, clicks and purrs Infant and young capybaras especially make a purring sound to maintain contact with the group.

Capybaras bark to alert the group when predators are seen. The capybaras will all stand alert when they hear this bark. If the danger is close and the caller continues to bark they will rush into the water and cluster together for safety with the young in the center of the group.

Small family groups of ten to twenty with one dominant male. They have a home range of about 25-50 acres. These groups are territorial and do not easily accept outsiders. The dominant male usually maintains his position by chasing the subordinate males, rarely by fighting.

In the dry season many of these groups may gather together around water.

In the wild they eat grasses and aquatic plants, melons and squashes. An adult capybara in the wild eats six to eight pounds of grasses a day.

It is hard for mammals to digest grass. To help them get all the nutrients from their diet, capybaras need special adaptations. One is a large fermentation chamber in the intestines called the cecum - this is like our appendix, but useful (unlike our appendix.) Another is that capybaras eat some of their own droppings. This is called coprophagy (which sounds so much more scientific than 'eating poop.')

Male capybaras can tell that a female is ready to mate by her scent. They mate in the water. Females are pregnant for about five months.

Usually four or five babies are born in a litter, weighing three or four pounds. They are born on land. They will join the group as soon as they can walk to follow their mother, about three or four days after birth. The babies can see soon after birth and can eat grass after only one week. They nurse for about 16 weeks and stay with the mother about a year. The young in a group stay together and the females will nurse infants other than their own.

Males reach sexual maturity at about 18 months and females at a year.

Jaguars, anacondas, and caiman (a reptile similar to alligators and crocodiles). Infant capybaras may also be eaten by foxes, vultures, and feral dogs.

People eat capybaras and their skin is made into leather. They are hunted in the wild and also raised on ranches. The meat tastes like pork with a hint of a fishy flavor.

In Venezuela, the Catholic Church allows people to eat capybaras during Lent, when usually only fish may be eaten.

Wild capybaras live 8 to 10 years. In captivity some have lived over 12 years.

Capybaras are not listed as an endangered species. They are intensively hunted in some areas but are still common in much of South America. In some countries, where they were almost eliminated by hunting, hunting is now restricted.

Ranchers fear that capybara will compete with their domestic animals such as cattle. But studies have shown that capybaras prefer short vegetation near water, while cattle prefer taller, drier grasses.

Bibliography

Walker's Mammals of the World.

Desmond Morris, The Mammals.

MacDonald, Encyclopedia of Mammals - Article on capybaras by Emilio Herrera

Alexandria Manera, Capybaras. (Scientific consultant Emilio Herrera)