What is the largest rodent, often active at dawn and dusk?

The largest rodent, often active at dawn and dusk, is the capybara.

The capybara (Hydrochoerus hydrochaeris) is a semiaquatic herbivore native to much of South America. It lives near rivers, lakes, marshes, and flooded grasslands, where its partly webbed feet and streamlined body help it escape predators in water. Adults commonly weigh 35–66 kilograms, although exceptional individuals can be heavier.

Capybaras are mainly crepuscular, meaning they are most active around dawn and dusk. This schedule helps them avoid the hottest part of the day and reduces exposure to predators. They graze on grasses and aquatic plants, and their continuously growing incisors are useful for cropping tough vegetation.

A common mix-up is confusing the capybara with the beaver or nutria. Beavers are also aquatic rodents, but they are smaller and are famous for building dams. Nutria resemble smaller capybaras but belong to a different genus. The capybara is closely related to guinea pigs and rock cavies, making it a giant member of that broader South American rodent group.