Capybara Hydrochaeris hydrochaeris

H. hydrochaeris is the single living species and genus and is the largest living rodent. Head and body lengths of H. hydrochaeris range from 100-130 cm and the tail is vestigial. Shoulder height can reach up to 50 cm and weights average between 27 and 79 kg. The hair is very sparse and coarse. Coloration is reddish brown to gray above and yellowish brown below. There may be some black coloration on the face, outer surface of the limbs and rump. Adult males have a large, bare patch on the snout which contains an enlarged sebaceous gland. The head is large and broad with relatively small, rounded ears. The eyes a small and placed fairly far back on the head. The muzzle is large with an enlarged upper lip. The front feet each have four digits and the back feet have three each. Females have five pairs of ventral mammae.

H. hydrochaeris inhabits densely vegetated areas around ponds, lakes, rivers, streams, marshes, and swamps. There is no permanent den, but rather the Capybara uses thickets for shelter. Where undisturbed, Capybaras are active during the morning and again in the evening, resting in shallow depressions in the ground in the heat of the day. In areas where H. hydrochaeris is disturbed by humans, activity is primarily nocturnal. It runs similarly to a horse and, if pursued, will enter the water swimming and diving with ease, the eyes and nostrils being the only visible body parts.

The diet consists mainly of grasses and is often seen grazing among cattle, It also consumes aquatic plants, grains, melons, and squashes.

Capybaras live in herds comprised of a breeding pair of animals to several breeding pairs and their offspring. There is generally a dominant male in the herd creating an aggressive hierarchy which is continually challenged. Vocalizations include low, clicking sounds indicating contentment; sharp whistles; abrupt grunts; and weak barks.

Breeding seasons vary throughout the range. Mating occurs year round in Venezuela, peaking around April and May just prior to the beginning of the rainy season. In Argentina, October is the preferred month, also just before the rainy season there. Usually, one litter is produced each year, though if conditions are favorable, there may be two. Gestation is between 149 - 156 days. Litter sizes range from 1-8 offspring, averaging 5 young. The babies weigh about 1,500 grams and the mother lactates for about 16 weeks. The young are precocial, able to follow their mother and eat grass soon after birth. Life span in the wild is 8-10 years.

H. hydrochaeris is found in E Panama, E Venezuela, the Guyanas and Peru, south through Brazil, Paraguay, NE Argentina, and Uruguay.