Hydrochoerus hydrochaeris - Capybara

Skull Pictures:

Dorsal        Ventral 

Lateral        Dentary

Photos by Christopher Yahnke, collection of the Field Museum of Natural History

Description:

Hydrochaeris hydrochaeris, the Capybara, is the largest member of the Family Rodentia.  It has short limbs ending in perissodactyle feet and moderately webbed digits.  The forefeet are characterized by having four digits while the hind feet have three.  Both fore and hindfeet’s nails are hoof-like, round, and thick. (Mones and Ojasti 1986) Unlike some rodents the capybara does not have a tail.  (Kato 2002) The Capybara has a broad head with short rounded ears, a large snout, and small widely separated nostrils.  This large rodent is covered in course hair that measures from 30-120 mm.  It ranges from dark brown to reddish and light brown to light yellowish gray.  The hair covers sweat glands that are unique to the capybara and make it the only rodent to have sweat glands on haired surfaces.   Hydrochaeris hyrochaeris weighs in between 35 to 65.5 kg on average. Males and females are distinguished (externally) by the nasal glands that are present in males (their presence indicates the capybara is sexually mature (Kato 2002)) and by the six pairs of ventral mammae the females possess.  The genitals of both sexes are hidden by anal sacs making it very hard to tell the sexes apart based on external genitalia.  The incisors of the males are generally larger and broader than those of females that are the same age.  (Mones and Ojasti 1986)

Distribution:

In general the Capybara is found from Panama down to northern Argentina.  It dwells in a variety of habitats, but is generally found near a water source (standing or running).  The capybara can also be found in lowland rainforests, dry forests, scrub, grasslands near water, areas with seasonal flooding, and areas with permanent water sources. (Ziegler, Unger, Feiler, Kraft 2002)  Their home range is approximately 10 to 15 hectares depending on the area, vegetation, and distance to a water source.  (Lord 1993)

Specifically in Paraguay the exact distribution is not clear when referring to the Gran Chaco area.  The upper Chaco (the northwestern area), also called the Dry Chaco, is considered an area where capybaras are very unlikely to be found.  Areas in Paraguay containing the Paraguay/ Parana rivers are better suited habitats for the capybara.  These rivers primarily run outside of the Dry Chaco.  It is cited in Ziegler, Unger, Feiler, and Kraft 2002, that the capybara does inhabit eastern and southern Dry Chaco areas, which contradicts the theory that the species doesn’t occur in the Dry Chaco.  The exact habitat and range of the capybara in the Dry Chaco is still being researched. (Ziegler, Unger, Feiler, Kraft 2002) (Mares 1982)

Ontogeny and Reproduction:

The capybara becomes sexually mature when it reaches a body mass of 30 kg which usually correlates to age 1.5.  The females usually have between one to eight young per gestation.  Paraguay’s capybaras generally have between one to four young; making their litter size smaller than capybaras in other regions.  Mating generally occurs around the onset of the rainy season which begins about April or May.  If the habitat is good capybaras may breed more than once a year. (Mones and Ojasti 1986)

The gestation period lasts a proximally 120 days which puts parturition in September to November. (Kato 2002)  Capybaras do not give birth in a nest, as some rodents do, but give birth anywhere in their habitat where cover is available.  In areas with little to no cover the young are susceptible to predation from avian predators.  Predators of young include: caracaras, black vultures, and caimans.  The young are born with a complete fur covering and complete permanent dentition.  They will suckle off the mother’s mammae for three to four months, but milk is not their main source of nutrients.  Grasses are the major contributor to the capybara’s diet in both young and adults.  (Mones and Ojasti 1986)

Ecology and Behavior:

The capybara primarily occupies habitats that contain water.  They can be found along most riverbanks, swamp land, wetlands, forested areas, and former riverbeds.  As long as there is a source of water for the capybara to use they will occupy that area.  Capybaras use water for drinking, wallowing, and for protection against terrestrial predators. They also use the water as a way to cool themselves when the temperatures are hot (the density of their sweat glands is low resulting in a limited ability to cool themselves by sweating). The mud near the water source is used as a defense against infestation by acarids. (Lord 1993)

Capybaras require land for grazing and dry land to rest upon.  During the rainy season capybaras will use the full area of their habitat and spread out to graze.  When the dry season returns they congragate to the water source in response to the lack of resources and food.  The dry season usually also brings the reduction of the capybara population due to starvation, increased predation (as a result of the increased capybara population during the rainy season), and disease.  (Mones and Ojasti 1986)

In general the capybara will take in about 70 grams of grass a day from grazing.  They are selective grazers and tend to select plants rich in protein. Capybaras eat both terrestrial and aquatic plants during their grazing periods.  Once the plant is eaten the capybara swallows; later while resting it will regurgitate its food and masticate.  Capybaras have a single chambered stomach unlike many mammals that practice rumination.  (Lord 1993)   During the dry season, when food sources are scarce, capybaras may move into livestock areas and compete with them for food resources.  (Mones and Ojasti 1986)

Capybaras can run, walk, and swim.  Even though they are rodents they are excellent swimmers and divers.  Young capybaras tend to stay out of the water.  Their behavior suggests that they are aware of the dangers in the water and prefer to graze on land.  (Lord 1993)  Capybaras can only run for 300 meters and tend to walk from grazing area to grazing area in a straight line along paths the herd has established.  (Mones and Ojasti 1986)

The herds range from one pair, to a family, to even complex groups with many adults (male and female) and their young.  Size of capybara herds change throughout the year; medium size (5.6) during the rainy season and highest in the drier months (15.9).  There is usually one dominant male, a few adult females (ranked according to their weights), their offspring, and a few subordinate males making up a herd.  (Mones and Ojasti 1986)  The subordinate males tend to stay on the edge of the core social group (in small groups of their own numbering two to four) and are often the target of the dominate males pursuits and aggression.  These same dominate males are never seen acting with aggression toward females, young, or infants.  Young capybaras do play and act with aggression toward one another and are often seen mock copulating with other litter mates. (Lord 1993)  

Mating rituals entail a male closely following a female on shore and in the water.  When she stops in the shallower water he mounts her for six to ten fast thrusts. This act can be repeated many times with the same or a different partner.  (Mones and Ojasti 1986)   It ends with the female capybara retreating from the male. (Lord 1993) Mating occurs during the rainy season, but in plentiful habitats it may occur more than once a year.  (Mones and Ojasti 1986)

Marking the territories of the capybara is the responsibility of the dominate male.  He uses the sebaceous glands on his snout and rubs bushes, stems, and plants.  Females, young, and subordinate males also use their sebaceous glands to make rubbings, but don’t do it as frequently as dominate males.  Urine is also used as to mark the territories of the capybara.  Both males and female use sacs located next to the anus to urinate on brush and other plant material.  Marking aids the herd by alerting other capybara groups (groups tend not to intermingle) to their territory and helps the herd itself stay within its own territory.  (Lord 1993)

Capybara calls are unique to the rodent.  When a predator is close or approaching they will let out a loud bark.  This will continue until the predator leaves or the capybaras retreat into the water for protection.  Whistle calls are made by young or infants when in need of their mother and will not terminate unless the mother is seen and returns.  Adult females also make this call when seeking an adult male.  Similarly the female will not stop until the male has begun to approach.  Lastly the “chuckle” is heard among members of the heard (adult females and young) while traveling together in a group.  (Lord 1993)

Remarks:

Adult capybara’s have very few predators; the main one being humans.  Capybaras are hunted (often over hunted) for their hides, meat, or just for being a rodent and a pest.  South Americans harvest 10,000+ hides annually for items such as gloves, belts, shoes, handbags, and many other leather pieces. (Mones and Ojasti 1986)  Capybara meat is considered below standard in most areas, but a few select areas in South America (such as Venezuela) see the meat as a great source of protein. (Mones and Ojasti 1986)  The fat from the capybara is also used for medicinal purposes such as respiratory illnesses. (Kato 2002)  It is for these reasons that many ranchers welcome the capybara onto their ranches and expect to make a profit from them living on their land. 

(Mones and Ojasti 1986)

Literature Cited:

Mones, Alvaro. and Ojasti, Junani. Hydrocoerus hydrochaeris. June 1986. American Society of Mammalogists.  Mammalian Species No. 264, pp. 1-7, 3 figs.

Lord, R. D. (1993):  A Descriptive Account of Capybara Behavior.  Studies on Neotropical Fauna and Environment 29, (1994), pp.11-22

Ziegler, Thomas. Unger, Jakob. Feiler, Alfred. and Kraft, Richard. Faunistische Abhandlungen. May 2002. On the occurrence of the capybara, Hydrochoerus hydrochaeris (Linnaues, 1766) in the Dry Chaco of Paraguay (Mammalia: Rodentia: Hydrochoeridae), pp. 424-429

Mares, Michael A. and Genoways, Hugh M. 1982. Mammalian Biology in South America. Pp. 393

Neris, Nora. Colman, Flaviano. Ovelar, Enrique. Sukigara, Naozumi. Ishi, Nobuo.  2002. Kato’s Data Book on Larger Mammals of Paraguay, Distribution, Population Trends and Utilization.  pp. 134

Reference written by Kathleen Stewart, Biology 378 (Mammalogy), University of Wisconsin – Stevens Point.  Edited by Chris Yahnke.  Page last updated August 8, 2005.