Adult extant (living) forms, of capybaras can be up to 25 inches tall (at the shoulder), 4.3 feet long, and up to 100 to 175 pounds (50 to 79 kg) in weight. Their bodies are covered in short brownish hair, and they have almost no tail (only a vestigal one). They have short legs (the hind legs are slightly longer than the front legs). There are four toes on the front legs and three toes on the back legs. Their face is rather long, in order to accommodate all their teeth. They also have blunt snouts.
Their feet are slightly webbed feet, and capybaras are superb swimmers. Like hippos, they have their eyes and small ears near the top of their head, thus they can swim also completely submerged. They live in densely forested areas (jungles), as well as on savannas near lakes, rivers, and wetlands/swamps. They are shy, social animals and live in herds up to 100 individuals, but usually only 10 to 20. Their life expectancy is 8 to 10 years. They are hunted for their hides and meat. They are also killed (sadly) as vermin. Some people keep them as pets.
Lunch time for a pack of capybaras at the Los Angeles Zoo. This picture was taken in the early 1980’s by the author. Capybaras are vegetarians. They are shown here eating cabbage or lettuce heads. Notice that the attendant is wearing very thick gloves (capybara front teeth are like sharp chisels).
Right-side view of a capybara skull. The mouth is large because the jaws are highly arched, which allows for a lot of grass to be held there until it moves onto the cheek teeth (the premolars in front and the molars in back), which do the grinding of the grass. Capybara are “mowing machines,” and their teeth are the business end of this “machine.” The upper jaw incisor teeth are thicker and shorter. The lower jaw incisor teeth are very long and projecting. In unison, the lower and upper incisors work like scissors, which is very efficient cutting of grass.
Like all rodents, their incisors grow continuously because they get worn down so fast by chewing mainly on grasses (rich in silica), aquatic plants, and reeds. These slightly curved teeth have a sharp leading edge, thereby enabling the teeth to efficiently nip/snip plant material.
The back (or cheek teeth) (molars and premolars) of capybaras consist of vertical enamel plates stacked closely together. They become narrower toward the front of the jaws and somewhat slanted. The check teeth also have a very distinctive and complicated surface design consisting of very narrow projecting ridges extending from top to bottom along both sides of these teeth. The back molars are also taller and more massive that those in front. The cheek teeth, which also grow continuously throughout life, show variation in their shape throughout the life of an individual, thereby making it difficult to identify a species if it is based only on the shapes of its teeth. Early workers overestimated the number of species as being 33. Modern workers using molecular phylogeny studies have greatly reduced this number (e.g., in one geographic region, seven species are now recognized as a single species).
Capybaras have also what is called hypsodont teeth (high-crowned with enamel extending below the gum line, providing extra hard material for wear and tear). The dental formula for capybaras is 1.0.1.3/1.0.1.3, which is a short-hand way of indicating the type and number of teeth on the upper jaw (= the first four numbers), as well as on the corresponding lower jaw) (= the second four numbers). They have 10 teeth on the left side of the mouth and also 10 teeth on the right side of the mouth; thereby making a total of 20 teeth. In sum, there are four incisors, no canines, 4 premolars, and 12 molars in the entire mouth. The gap between the incisors and the cheek teeth is called the diastema. Horses have a diastema too, as well as some other animals. The molar teeth of capybaras are sturdy and well designed for chewing plants.
The scientific classification of capybaras is in a state of flux, but most workers use the following divisions: order Rodentia; suborder Hystricomorpha; family Caviidae; and genus Hydrochoerus. The genus name is Latinized and derived from ancient Greek hydro (“water”) + choiros (“pig) because they like to be in and around water and resemble tail-less pigs. Although they are colloquially, but mistakenly, called “water hogs” or “water pigs,” those designations are grossly inaccurate because hogs/pigs are not rodents.
Capybaras belong to a group of rodents also referred to as caviomorphs, which includes guinea pigs, pacas, rock cavies, chinchillas, and porcupines (especially the New World ones). One of these caviomorphs is most likely the direct ancestor of capybaras.
The earliest known rodents in South America are of late middle Eocene in age (approximately 40 million years old), but they were not capybaras. The earliest capybaras belong to genus Hydrochoerus and they are 9.5 million years old (= early late Miocene age) (see diagram below) and are found in the Buenos Aires Province of South America. The origin of capybaras occurred just after the middle Miocene climatic optimum, which was a time of world warmth. Hydrochoerus represents the main lineage of capybaras. There are two living species of this genus: Hydrochoerus hydrochaeris Linnaeus, 1766, which lives in northern Argentina (but not Chile) to Colombia and Venezuela. The other living species is Hydrochoerus isthmius Golden, 1912 which lives in northern Columbia, northeast Venezuela, and Panama.
Perhaps the largest rodent of all time was a giant form of the caviomorphs called pakaranas (also called “pacaranas”), which are normally of small size and have relatively long tails. The giant form lived during Pliocene to early Pleistocene time in the southern coastal part of Uruguay, just south of Brazil in South America. Some scientists believe, however, that it is the same animal as the rodent Phoberomys, known from the late Miocene in Venezuela. The currently accepted scientific name of this giant is Josephoartigasia monesi. It belongs to family Dinomyidae. Individuals have been estimated as having a height of 1.5 m (5 ft.), a length of 3 m (10 ft.), and weighing approximately up to a ton. That would make them about the size of a rhinoceros, a bear, or a pickup truck. The image of this particular fossil capybara is minted on the “two-pesos” coin of Uruguay. This rodent is based on isolated teeth and a few skulls, thus its true size cannot be determined with total confidence.
As depicted in the time/paleogeographic diagram shown below, during the GABI (the Great American Biotic Interchange), South America became connected to North America via a land bridge in Panama during Pliocene-Pleistocene time (starting about 3.5 million years ago). That is when Neochoerus, a genus (now extinct) of capybaras evolved. Its fossil remains have been found in Central America, Arizona, southern Texas, Florida, and South Carolina. Individuals reached a size about 40 percent larger (e.g., 250 pounds total) than living capybaras. Today, there are some invasive occurrences of capybaras primarily in southern Florida. These were introduced by the release/escape of pets), but to date, breeding populations have not been confirmed there.
Biogeography of capybaras versus geologic time.
Research and drafting by R. Squires (Fall, 2022). [mya = millions of years ago]
References:
Britannica.com---An online source with great videos. FREE.
Lawlor, T.E. 1979. (Illustrations by K. Simpson). Handbook to the orders and families of living mammals. Second edition. Mad River Press, Eureka, California. 327 pp.
Savage, R.J.G. and M.R. Long. 1986. Mammal evolution, an illustrated guide. British Museum of Natural History. 259 pp. [out-of-print?, but a very helpful book].
Wikipedia.org---especially useful for looking up the scientific names of the animals/fossil names and especially for providing links to the literature.
