The capybara, often affectionately referred to as the “water pig,” is the largest living rodent species on Earth. This semi-aquatic mammal has captivated people with its calm demeanor and unique physical traits, allowing it to thrive across the diverse wetlands of South America. Its status as a giant among rodents and deep connection to water make it a fascinating subject.
The World’s Largest Rodent
The capybara (Hydrochoerus hydrochaeris) holds the title as the world’s largest rodent, a classification it shares with smaller relatives like guinea pigs and rock cavies. Adult capybaras can reach a length of about 1.3 meters (4.3 feet) and stand up to 0.6 meters (2 feet) tall at the shoulder. They typically weigh between 35 and 66 kilograms (77 to 146 pounds), though some large females can weigh up to 79 kilograms.
The capybara’s geographical range spans nearly all of South America, extending from Panama down to northern Argentina, wherever forest or savanna meets permanent water sources. The common name “capybara” originates from the Guarani word ka’apiûara, which translates to “master of the grasses,” reflecting its primary diet. Its scientific genus name, Hydrochoerus, comes from the Greek words for “water” and “pig,” directly inspiring the nickname “water pig” due to its barrel-shaped body and amphibious lifestyle.
Life in the Water: Unique Adaptations
The capybara’s life revolves around water, which it uses for thermoregulation and defense. It possesses a coarse, thin coat of reddish-brown fur that lacks an insulating undercoat, allowing it to dry quickly and preventing it from becoming waterlogged. This specialized coat is necessary because the capybara’s skin can dry out in the sun, requiring frequent dips in water or mud wallows to stay healthy and cool.
Physical features are modified to enhance its aquatic ability, beginning with partially webbed feet. These adaptations provide superior propulsion for swimming and help the animal navigate soft, muddy banks. The front feet have four toes while the hind feet have three, each tipped with a strong, hoof-like claw.
The placement of the capybara’s sensory organs is a defining aquatic adaptation. Its eyes, ears, and nostrils are set high on top of its head, similar to a hippopotamus. This configuration allows the capybara to remain almost entirely submerged, with only its sensory organs breaking the surface to see, hear, and breathe.
This ability to hide while submerged is the capybara’s primary defense mechanism against land predators. When threatened, a capybara will plunge into the water and can remain completely submerged for up to five minutes. The ears can also be pressed flat against the head to seal out water, optimizing its ability to hide.
Social Structure and Diet
Capybaras are highly gregarious animals, rarely found alone, and typically live in family groups or herds of 10 to 20 individuals. These groups are structured around a dominant male, several adult females, subordinate males, and the young. During the dry season, when water sources dwindle, multiple smaller groups may aggregate into larger herds of up to 100 individuals around remaining pools.
Communication within these social units involves a range of vocalizations, including barks used as alarm calls, as well as whistles, purrs, and clicks for general communication and social bonding. They also utilize scent marking. Males possess a prominent scent gland called a morrillo on their snout, which is used to mark territory and signal dominance.
As strict herbivores, their diet consists primarily of grasses and aquatic plants, which they graze on during the cooler morning and evening hours. The fibrous nature of their diet necessitates a unique digestive strategy called autocoprophagy. They consume their own specialized feces to re-digest food and extract maximum nutrients, including beneficial bacteria and vitamins. Females typically give birth to a single litter per year, averaging four young. The precocial pups are able to walk and graze shortly after birth, and communal nursing is common within the herd.