The largest rodent in the world, living in South American rainforests, is the capybara.
The capybara (Hydrochoerus hydrochaeris) is a semi-aquatic herbivore native to much of South America. It prefers habitats near rivers, lakes, marshes, and flooded forests, where its slightly webbed feet and eyes, ears, and nostrils positioned high on its head help it move and hide in water.
Adult capybaras can grow to about 1.5 metres long and may weigh more than 60 kilograms, with exceptional individuals becoming heavier. They live socially, commonly in groups of 10 to 20, and communicate with whistles, barks, purrs, and other sounds.
A common mix-up is confusing the capybara with the beaver or nutria. Beavers are powerful dam-builders, while nutrias are smaller semi-aquatic rodents. The capybara is also related to guinea pigs, despite its much larger size. The extinct Josephoartigasia monesi was larger, but the capybara remains the largest living rodent.