The capybara is an efficient grazer, able to crop the short, dry grasses left at the end of the tropical dry season (3). Although the diet comprises mainly grass, it also includes aquatic vegetation, such a water hyacinths, as well as other plants, grain, and sometimes fruits (2) (3) (4). When alarmed, the capybara is capable of running swiftly over land, and often dives into water to escape (2) (4) (6). A strong swimmer, it is able to stay underwater for up to five minutes at a time (3) (6). The species is normally active morning and evening, resting during the heat of the day, but has apparently become nocturnal in areas where it is persecuted by humans (2) (4).
A social species, the capybara is typically found in family groups of around 10 to 30 individuals, comprising a dominant male, one or more females (which are often related), young of various ages, and one or more subordinate males. Most solitary individuals are male. Group size may depend on habitat, and in the dry season several groups may gather around dwindling pools, forming temporary aggregations of up to 100 or more animals. However, when the wet season returns, these aggregations split into the original groups that formed them (3) (5) (8). All adults in a group help defend the territory against intruders, and regularly scent mark the area using secretions from anal scent glands. These secretions may also be used for individual recognition, as the proportions of chemicals they contain differ between individual capybaras (3) (8).
Capybaras mate in the water (3) (6). The female usually gives birth to a single litter each year (4) (6), at the end of the rainy season, after a gestation period of around 150 days (3) (8). Usually, up to eight young are born, and are highly developed at birth, able to follow the female and even eat grass within the first week of life (3) (4) (5). Weaning takes place at around 16 weeks (4), although milk is a relatively minor part of the infant's diet compared to grass (5). All young within the group tend to stay together in a crèche, and may suckle from any nursing female (3) (8). The capybara reaches sexual maturity at around 12 to 18 months, and may live for up to 10 years in the wild, or to 12 years in captivity (3) (4).