|A small Capybara shaking itself off as it climbs out of the water.|
Capybaras are the largest members of the order Rodentia (rodents), growing to weigh from sixty to one hundred seventy pounds. They are found in central and eastern South America, in the American Rainforest, and in the savannas. Capybaras are semi-aquatic, with webbed feet and a respiratory system that allows them to swim underwater for five minutes without having to go up for air. Despite their rodent teeth, capybaras are herbivores and primarily eat grass. Though one would think that people would be afraid of such a monstrous rodent, many keep capybaras as pets, just like a household mouse or dog.
Capybaras are the largest rodents in the world, standing 1.5 feet tall, three to four feet long, and weighing from sixty to one hundred seventy pounds.  Their bodies are heavy and barrel-shaped, and their heads are short, relatively large, and broad. Their muzzle is heavy and squared at the end, with an enlarged upper lip. On the dorsal side of the muzzle are small external eyes, ears, and nostrils. The unique positioning of their sensory organs enables capybaras to function properly without exposing much of their bodies to predators while swimming. 
Like all rodents, they have sharp teeth that never stop growing. Capybaras have twenty teeth total, two pairs of which are large rodent incisors, and another four pair being molars, located on each side of the lower jaw. Capybaras spend a lot of time chewing on tough grasses to keep the teeth from growing too long. 
They have short, somewhat stubby legs to support their stocky bodies. Their front legs are slightly shorter that its hind legs, though that does not seem to hinder its balance. Their front legs have four toes whereas the hind feet have only three. Each toe is tipped with a hoof-like claw, which are partially connected together by webbing.
Capybaras also have an extremely short, barely visible tail, located on their rear end. The tail has no known use.  In mature males, a bare raised area on the top of the snout contains enlarged sebaceous, oil secreting glands, which produce odorous secretions. The dominant male is usually found to be the one with the largest scent gland. 
Their fur is most often a brown- red color on the top, and a brown- yellow color on its underside. It also appears to be prickly, but is actually fairly soft. The prickly-looking effect of the fur is the result of the sharp angle at which the capybara’s fur protrudes from its body. Their coat of fur is relatively thin, which allows the fur to dry quickly after its removed from the water.
The capybara’s skin is quite extraordinary in that the epidermis is covered in folds of tissue; this creates a larger area from which the capybara can facilitate its body’s cooling and heat exchange. Although the capybara has many sweat glands distributed all over its body, they are not particularly suited to general thermal cooling. Because of the capybara’s lack of effective sweat glands, it is forced to frequently swim or wade in water to reduce its body temperature. 
Grasses are difficult for most mammals to digest, the capybara included, so the capybara’s digestive system has a few adaptations to make digestion easier. An example of these adaptations is a large fermented chamber in the intestines called the cecum. Capybaras also engage in coprophagy, the consumption of their own feces. These feces provide a rich source of nutrients.
Capybaras are social creatures, living in groups of six to twenty, although groups of one hundred or more have been reported. The group hierarchy is composed of a dominant male, several adult females and their young, and several submissive adult males. The group is usually made up of family members and outsiders are rarely accepted into the herd. 
Males will reach sexual maturity at eighteen months, while a female will become mature at only twelve months. They reproduce sexually, usually once a year, but in order for reproduction to occur, the conditions must be perfect.  Mating usually occurs during the rainy months of April and May. A male detects that a female is ready to mate by her scent.  When a male detects a ready female, he will follow her out into the water where he will mount her and they will copulate. The female capybara’s gestation period lasts about one hundred fifty days.
Before a female gives birth, she will leave the group and find somewhere private to birth her two to eight young. Capybaras are viviparous, which means that the embryo develops inside the mother, feeding off of nutrients from a tube, and are born alive. After she has given birth, the female will return to the group, followed three or four days later by her new pups once they learn to walk. Their pups are born weighing two to four pounds and are precocial, having fur, a full mouth of teeth, and being able to see.  The young travel around the herd in their own group, and after only one week they are able to feed on grass. The pups will nurse from any female in the group until they are weaned at sixteen weeks. 
The young capybaras will stay with their mother for about a year, after which they will form their own herd, become a part of their mother’s heard, or venture out alone, which usually results in death. Life expectancy for a capybara in the wild is an average of eight to ten years, and in captivity, up to twelve years. 
Capybaras are found throughout the Amazon Rainforest and savanna in South America Their habitat includes the countries of Brazil, Uruguay, Paraguay, Bolivia, Peru, Ecuador, Colombia, Panama, Venezuela, Guyana, Suriname, and Guiana.
Being semi-aquatic, they are found frequently in the dense vegetation surrounding rivers, lakes, marshes, or ponds.  The water sources dictate the location of their homes because they provide shelter, thermoregulation, food, and also affect mating. Shoals, sandbars with grass, are a staple for the capybara. The shoals provide a plentiful source of food, and also a cool place to rest.  Capybara do not dig burrows; instead, they make little beds in the shoals or shallow parts of the dirt.  A shoal is also ideal for birthing and raising pups. 
They share their homes with many other animals such as water birds, anacondas, marsh deer, giant otters, anteaters, parrots, jaguars, and caimans. The capybara’s main predators are jaguars, anacondas, and caimans, large reptiles similar to alligators and crocodiles. Foxes, vultures, and wild dogs will often prey upon the infant capybaras.  Men also hunt capybaras for their meat and skin.  Because the capybara is an excellent swimmer, it can escape from its predators by diving into the water and hiding. 
Capybaras are herbivores, creatures that eat plants. Much of their time is spent grazing and searching for food, which is primarily composed of protein-rich grasses. A full grown adult will eat, on average, six to eight pounds of grass in one day. They will also eat water plants, fruits, and vegetables like melons and squashes. 
Giant Capybara Fossil
Today, capybaras are the world’s largest living mammals inhabiting South America. However, fossils of extinct species of capybaras were found in North America, Central America, the West Indies, and South America. In 1995, a partial skull in Pleistocene pond in Oceanside, San Diego County was the setting for the first discovery of capybara fossil remains. SDNHM (San Diego Natural History Museum) paleontologists found the fossil during construction excavations for a new shopping center on the south side of the San Luis Rey River Valley. The Oceanside specimen helped extend understanding of the ancient distribution of capybaras in North America. 
In January of 2008, a twenty-two hundred pound fossilized capybara was discovered in the face of a cliff in the mountains of Uruguay by an amateur paleontologist. The skull was unearthed by a team led by Andrés Rinderknecht, who conducts studies for the National Museum of Natural History and Anthropology in Montevideo, Uruguay.
The skull suggests that the rodent’s body was twice as heavy as the last largest known rodent, a giant guinea pig discovered in Venezuela that weighed fifteen hundred pounds in 2003.
The fossilized two-foot-long skull of the one-ton capybara that once roamed South America has been described by Dr. Rudemar Ernesto Blanco to be depicting a creature that was likely the size of a modern day bull. 
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