• Capibaras mate exclusively in water, and if a female does not want to mate with a particular male, she either dives or leaves the water. A female can refuse mating by diving or leaving the water.
• Dominant male capibaras actively guard females, but usually cannot completely prevent subordinate males from mating. The larger the group, the harder it is for a male to control all females.
• Capibara makes whistling sounds through its nostrils to signal males that it is ready to mate. During estrus, when the female's scent changes, she also attracts males this way.
• Young are born with open eyes and can swim within a few days.

Capybaras reproduce sexually, and the female carries young for about five months before giving birth on land; the young are born live, not hatched from eggs or larvae, and can walk and swim immediately after birth. A litter consists of two to eight capybara pups, and the female reaches sexual maturity between one year and three months and one year and eight months of age. Reproduction occurs with homogamy, always involving fertilization and without generational changes. The interval between successive litters is from ten months to one year and one month. Capybaras inhabit and develop on land, outside of bodies of water.