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family hydrochaeridae


Capybaras are the largest rodents in the world. An adult may weigh as much as 60 kg and stand 60 cm high at the shoulder. The family contains a single living species, but in the past other species existed, some much larger than modern capybaras, reaching or exceeding the size of a large bear. The family is found only in the tropics of South America north to Panama.

Capybaras have a heavy, barrel-shaped body. Their scientific name means "water hog" and indeed their bodies are hog-like, but they are rodents, not artiodactyls. And unlike hogs, they have short and deep heads. Their external ears and eyes are small; these and the nostrils sit high up on the rostrum, so that they lie above water level when the animal is mostly submerged. A capybara's legs are not long, and the front legs are shorter than the hind. Their tails are extremely short, appearing to be missing altogether. The forefeet have 4 digits and the hindfeet 3, and each toe is tipped with an almost hoof-like claw. Webbing partially connects the digits. The fur is coarse and sparse, consisting mostly of bristle-like hairs; the brown or gray skin can be seen through the hairs (which themselves are brown).

The skull of a capybara is very much like that of a guinea pig (Caviidae), except that it is very much larger and more robust. Capybaras are classified with the hystricognaths, but their jaws appear to have secondarily become almost sciurognathous. They are, however, hystricomorphous, with large infraorbital canals through which runs the medial masseteric musculature. Like the caviids, capybaras have a pronounced masseteric crest on the sides of the mandibles; this crest is separated from the toothrow by a deep groove. Capybaras also have unusually large paroccipital processes. Their auditory bullae are not enlarged. The toothrows converge anteriorly, so that the palate is shaped like an inverted "V." The zygomatic arches are robust, but the jugal does not contact the lacrimal.

The cheek teeth of capybaras are like those of no other mammals, distinctively flat crowned and hypsodont. The third upper molar is the most unusual, being extremely long and made up of a series of 9 or 10 transverse plates (loxodont). The dental formula is 1/1, 0/0, 1/1/, 3/3 = 20. The incisors are massive and chisel-like.

Capybaras are semiaquatic, living near ponds, rivers, or swamps and feeding on aquatic plants. They associate in groups of 10 or more individuals, and at times several groups may forage together, forming a much larger herd. These groups have a fairly permanent membership, consisting of of a dominant male, one or more adult females and their infants, and sometimes subordinant males. Capybaras are excellent swimmers, capable of diving and remaining beneath the surface for as long as 5 minutes. They also have the habit of submerging so that only their nostrils are above the surface. If threatened, their usual response is to flee into the water. Jaguars may have been their most important predators, but some are probably killed by anacondas and caimans.

A male capybara has a distinctive scent gland called a "morrillo" that appears as a dark, oval-shaped, hairless bump on top of its rostrum. Both sexes have large anal glands. They also use a number of vocal signals to communicate.

Capybaras are raised commercially in some parts of South America, providing both meat and leather to the farmer.

Families of Order Rodentia

Suborder Sciurognathi

Family Aplodontidae (mountain beaver, sewellel)
Family Sciuridae (squirrels)
Family Castoridae (beavers)
Family Geomyidae (pocket gophers)
Family Heteromyidae (kangaroo rats, pocket mice, and allies)
Family Dipodidae (birch mice, jumping mice, jerboas)
Family Muridae (familiar rates and other rodents)
Family Anomaluridae (scaly-tailed squirrels)
Family Pedetidae (spring hare, springhaas)
Family Ctenodactylidae (gundis)
Family Myoxidae (dormice and hazel mice)

Suborder Hystricognathi

Family Bathyergidae (mole rats, blesmols, and rats)
Family Hystricidae (Old World porcupines)
Family Petromuridae (rock rat or dassie rat)
Family Thryonomyidae (cane rats or grasscutters)
Family Erethizontidae (New World porcupines)
Family Chinchillidae (Chinchillas and viscachas)
Family Dinomyidae (pacarana, branick rats, false paca)
Family Caviidae (cavies and  guinea pigs)
Family Hydrochaeridae (capybara)
Family Dasyproctidae (agoutis, acouchis)
Family Agoutidae (pacas)
Family Ctenomyidae (tuco-tucos)
Family Octodontidae (degus, coruros, rock rats)
Family Abrocomidae (chinchilla rats, chinchillones)
Family Echimyidae (spiny rats)
Family Capromyidae (hutias, zagouties, cavies, Indian coneys)
Family Heptaxodontidae (Quemi, giant hutias)
Family Myocastoridae (nutria, coypu)

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