Capybaras

(Hydrochaeridae)

Class Mammalia

Order Rodentia

Suborder Hystricognathi

Family Hydrochaeridae

Thumbnail description
Large terrestrial and semi-aquatic herbivore rodent; the body is covered with coarse, reddish brown to grayish hair; underparts are lighter yellow-brown

Size
Head and body length 39.4–51.2 in (100–130 cm); shoulder height up to 19.7 in (50 cm); average weight 138.9 lb (63 kg)

Number of genera, species
1 genus; 1 species

Habitat
Lowland wetlands of forest, woodland, savanna, and open areas

Conservation status
Not threatened

Distribution
Range spans in lowlands from Panama throughout South America to Northern Argentina and Uruguay

Evolution and systematics

Capybaras of today do not differ essentially from those forms of the past. Many Pleistocene rodents, such as capybaras, have probably undergone little change in the past million years. Cenozoic fossils recovered from the Antilles island of Grenada differ from the existing capybara.

There is only one single living genus and species, Hydrochaeris hydrochaeris; some authors consider the smaller form of capybara living in Panama, western Colombia, and northwestern Venezuela (H. isthmius) as a separate species; other consider this form a subspecies, H. h. isthmius.

The taxonomy for this species is Hydrochaeris hydrochaeris (Linnaeus, 1766), Suriname. Other common names include "capivara" in Portuguese and "carpincho" and "chigüire" in Spanish.

Physical characteristics

Capybaras resemble agoutis but are much larger. The head is large and broad, the ears are small and rounded, the eyes located dorsally, the neck is robust and short, not differentiating in diameter from the head. The body is covered with coarse hair that is reddish brown to grayish, and lighter yellow-brown in the underparts. The capybara is the largest living rodent, with a pig-sized pregnant female reaching 176.4 lb (80 kg) in weight; head and body length is 39.4–51.2 in (100–130 cm); shoulder height is up to 19.7 in (50 cm); and average weight is 139 lb (63 kg).

The muzzle is truncate with an enlarged upper lip and large nostrils. The forefeet have each four toes and the hind feet three, all armed with short but strong claws. Feet are partially webbed to allow swimming. The coarse pelage is so sparse that it allows one to see the animal's skin. Females have four pairs of ventral mammae.

Adult males can be identified by their black sebaceous gland, a scent gland, located on the top of the muzzle, which is used to mark with essence plants and other substrates in their territory. The tail is very short and vestigial.

As an herbivorous rodent, the teeth are distinctive; the incisor teeth are white and shallowly grooved. The third molar

is longer than the other three molar teeth. The cheek teeth are modified and ever-growing.

Distribution

Capybaras occur in Panama, close to the Canal Zone, and on the east side of the Andes from Colombia, Venezuela, and the Guianas, throughout Brazil, Bolivia, and Paraguay, to Uruguay and northeastern Argentina. The original distribution range is wide but some local populations have been eliminated by hunting or by drastic habitat modification.

Habitat

Capybaras inhabit areas along rivers and streams, lakes, ponds, marshes, and swamps. There are at least three habitat components important for capybaras: water, grass vegetation, and a patch of forest or woodland. At least three regions are well known to harbor conspicuous concentrations of capybara populations: the llanos in Venezuela, the pantanal, mostly in western Brazil, and the Taim lowlands, in southern Brazil.

Capybaras are also abundant in the Amazonian floodplain, comprising all the countries forming the biome, but particularly Marajó Island, located at the mouth of the Amazon river.

In the pantanal of western Brazil there exist vigorous populations of capybaras. Flooding is the most important element to characterize the habitats of the pantanal. When the land dries out, grasslands and scattered pools appear. The capybara densities in these grassland fields during the dry season reach spectacular numbers due to the provision of feeding and reproductive habitats. During the floods, the capybara groups subdivide and are largely confined to the woodland and forest patches.

Capybaras are able to take advantage of modified habitats to increase their populations. They rapidly colonize areas surrounding artificial lakes formed by dams. They also explore habitats that may offer food, even with some degree of pollution, such as the Tietê River in the city of São Paulo. Sometimes they cause damage to plantations of corn, rice, manioc, and legumes, and may be hunted for that reason.

Behavior

Capybaras are social animals, usually living in family groups composed adult males, adult females, and young. Mean group size is six animals, but they exhibit variation in size during the year. In the pantanal, for example, the group size increases from the beginning of the year (rainy season) to the middle of the year (dry season). Groups of eight to 12 animals are relatively common.

The group composition is usually formed by a dominant full adult male, one or two full adult submissive males, two to four or more adult females, and the others are subadults and young. The dominant male in the group exhibits aggressive and hostile behavior to keep the other males submissive. Females in the group also display a hierarchy. The social behavior reflects group sizes. They are docile, quiet, crepuscular animals but may show activities during the day, except for some rest periods in their shelters in the forest, during the hotter hours of the day.

Ranging behavior is variable. The home range occupied by a given social group averages 200 acres (80 ha), but may be much larger in some cases, depending on the season of the year. This home range contains foraging area, patch of woodland or forest where the group rests and reproduces, and water where the animals swim. Neighboring groups may share parts of their home ranges, but maintain some core areas within these home ranges that are for the exclusive use of the group. In flooded areas, groups have larger ranges and core areas during the dry season than during the rainy and flooding season, a change that is associated with the reduction of

the feeding grassland habitat. During the dry season, larger groups are seeing feeding on the grassland seasonal fields. During the flooding season, the groups split into smaller groups, and disperse among the patches of the forest or woodland, using more of the water habitats of ponds or inundated areas.

Capybara groups in the wild have been observed displaying three different activities: foraging on grasses, sleeping or resting, and exhibiting social interactions. They display distinctive postures, movements, sounds, and activity patterns:

• Alert. The capybara remains immobile on its four feet or sitting, staying in whatever position it happens to be in at the time of the stimulus. The animal keeps its head raised, looking in one direction, with the ears erect. If an intruder continues to approach, the capybara barks like a dog, jumping into the water or running away.
• Grazing. The capybara grazes, moving slowly while foraging, sometimes raising its head to check its surroundings.
• Lying. Usually the animal lies down with its head erect while resting.
• Sleeping. The animal sleeps intermittently during the daylight hours and evening in wooded areas.
• Sitting. This is also a resting posture, common on the river banks.
• Swimming. Capybaras are good swimmers and divers.
• Intimidating. One dominant male or female circles an intruder or submissive capybara in order to impose its dominance or to ward off an approach.
• Fighting. Two animals in an upright position embrace each other and engage in a fight or a male and female exhibit courtship.
• Contacting. During the encounter between two animals one may actively initiate contact, either sexual or antagonistic. The male may inspect the sexual receptivity of a female by nasal-genital contact.
• Mounting. The female swims back and forth in the water, pursued by the male, and when she displays a receptive position, the male mounts.
• Maternal care. Involves nursing with a mother and her young.

• Marking. The male rubs his snout gland up and down a stalk, or the animal straddles a stalk in order to rub it with its anal scent gland.

Male to male aggressive interaction is the most common display seen in the field. Subadults of either sex are always subordinate to adults of either sex. The dominant male of the group initiates the attack. Some subadults suffering attacks are excluded from the group and become satellite animals. These animals suffer stress and are subject to being weak, sick, and killed by predators.

The males compete more strongly for access to breeding partners than do females; a female's reproductive success depends on her ability to acquire food. The females spend a great deal of their time caring for young of different ages, who move from one female to another. The females suckle young in a crèche-behavior fashion.

Feeding ecology and diet

Capybaras invest a great deal of their time in feeding behavior. In Brazil, the states of Minas Gerais and Goiás are

separated by a river. People living in two small villages, of the river, are rivals. The villagers on the Minas Gerais border, where there are grassland fields, say that Goiás is so bad that capybaras prefer to feed on their side. The villagers in Goiás claim that Minas Gerais may have some good food but Goiás is a nicer place to live, since the capybaras cross the river to sleep there.

Apart from the beliefs of human rivals, capybara ranging behavior is based on a daily need for food and shelter. The Portuguese priest José de Anchieta, traveling through Brazil in 1560, wrote about the animals named by indigenous people as "capivaras," which means "herb feeders." Another Portuguese explorer, Fernão Cardim, wrote in 1584, about the "water pigs" known as capivaras that eat herbs and fruits found along the rivers.

Capybaras are very selective in food items they prefer. The diet composition varies from the dry season, when more pasture is available, to the flooding season, when they can feed upon floating plants. Preferred food items, such as protein rich grasses, tend to be more seasonal than poorer food items. During the dry season, natural pasture in lower areas is abundant and is preferred by capybaras. Capybaras may re-ingest their own fresh feces (coprophagy) in order to maximize the absorption of nutrients.

Young are precocious, travel on the back of their parents when they swim, forage on grasses with few days of age, and suckle their mother or other lactating female in their social group.

Reproductive biology

Depending on the quality of the habitat, capybaras breed throughout the year, presenting a peak of reproduction when more feeding grounds are available. Copulation usually occurs in the water. The forest and woodland provide shelter from midday heat and a resting place, as well as a birth place. The gestation period is about 147 days and it is possible that this length may be influenced by environmental and social variables. Litter size is one to seven, averaging 3.5 neonates,

each weighing about 3 lb (1,400 g). Lactation period is about 10 weeks. However, at certain times of year, it is possible to observe a female with 10 or more young of different ages and sizes. It is believed that the group of young are relatives, and one lactating female takes turns caring her own young and those of her sister or relative. The sex ratio for the population in the field averages one male to three females. At birth, the sex ratio averages one male to one female, but due to the social structure, this relation changes. As soon as the subadults begin to attain sexual maturity, some are excluded from the group, mainly males, by the dominant males. These excluded subadults become satellite or solitary individuals. Under stress, these animals are susceptible to diseases.

Before capybaras die, their bodily appearance declines visibly. A sick individual is often isolated from the group. In addition,

capybaras are preferred prey for jaguars and young are captured by anacondas and other predators.

Conservation status

Capybaras are common animals distributed over a wide range. Thus, they are not considered threatened, although in many places they, have been extirpated due to human influence, mainly hunting. They are very tolerant of habitat modification and, when that change benefits the offering of food and reproduction niches, the population increases, if they are not otherwise disturbed.

Significance to humans

The first Portuguese explorers traveling through Brazil in the sixteenth century reported that they learned from the local indigenous people that capybara meat was consumed and considered beef or sometimes fish. In fact, in the llanos of Venezuela, people eat capybara meat during Lent, in place of fish, as a religious and cultural tradition. Throughout the Amazon basin, capybara is consumed by local people as a real meat, since people living along the rivers consume fish daily and sometimes appreciate a different kind of meat.

There is a growing interest in the management of capybaras to commercially exploit their meat and skin (the leather is valuable). In some countries such as Venezuela and Brazil two options for exploitation were identified: management in natural areas and raising or farming in enclosures.

In wild populations of higher densities in good habitats, such as the llanos of Venezuela, it is possible to establish a harvest quota, based on the fact that part of the population would disappear due to disease and predation. Harvest quotas could be increased through the implementation of programs to control mortality caused by diseases. The predation in ranches is low and the capybara population can increase in number. The construction of ponds and the offer of food can also increase population levels for management and sustainable use.

There are some authorized farming structures to raise capybaras in Brazil. However, the final cost of the meat is still higher than the traditional beef.

Some health researchers, working with free ranging capybaras that reached the plazas in the city of Campinas, Brazil, by traveling through small creeks, discovered that the animals can pose a potential threat to humans. The ectoparasites they carry with them into the city, mainly ticks, could potentially transmit bacterial or viral diseases to humans.

Resources

Books

Alho, C. J. R., Z. M. Campos, and H. C. Gonçalves. "Ecology, Social Behavior and Management of the Capybara (Hydrochaeris hydrochaeris) in the Pantanal of Brazil." In Advances in Neotropical Mammalogy, edited by K. H. Redford and J. F. Eisenberg. Gainesville, FL: Sandhill Crane Press, 1989.

E. Herrera. "Reproductive Strategies of Female Capybaras: Dry-season Gestation." In The Behaviour and Ecology of Riparian Mammals, edited by N. Dunstone and M. L. Gorman. Cambridge: Cambridge University Press, 1998.

Periodicals

MacPhee, R. D. E., S. Ronald, and D. Michael. "Late Cenozoic Land Mammals from Grenada, Lesser Antilles Island-Arc." American Museum Novitates 2000, no. 3302 (2000): 1–20.

Moreira, J. R., D. W. Macdonald, and J. R. Clarke. "Alguns Aspectos Comportamentais da Reprodução da Capivara." Revista Brasileira de Reprodução Animal 25, no. 2 (2001): 120–122.

Rowe, D., and R. Honeycutt. "Ecological Correlates, Molecular Evolution and Phylogenetic Relationships within the Rodent Superfamily Cavioidea." Molecular Biology and Evolution 19, no. 3 (2002): 263–277.

Thomas, Z., U. Jakob, F. Alfred, and K. Richard. "On the Occurrence of the Capybara, Hydrochoerus hydrochaeris (Linnaeus, 1776) in the Dry Chaco of Paraguay (Mammalia: Rodentia: Hydrochoeridae)" Faunistische Abhandlungen Dresden 22, no. 2 (2002): 423–429.

Cleber J. R. Alho, PhD