The capybara is the largest rodent in the world.
Capybara (Hydrochoerus hydrochaeris) in the Toronto Zoo.
The capybara looks like a gigantic guinea pig to whom they are closely related. The capybara is semi-aquatic and it can only escape the heat on a warm day by being submerged in water. Capybaras are vegetarian and mostly eat aquatic plans, tree bark, fruits and leaves.
Just like us humans, and its cousin the guinea pig, the capybara also lacks the ability to synthesize vitamin C and can get scurvy — which is unusual as most animals produce their own vitamin C supply.
Just like the guinea pigs, capybaras do like to be petted and can make a good pet if one has the appropriate setting to accommodate a rodent that weighs about 50kg and requires its own swimming pool.
Capybaras.
Further Readings:
Adaptations of the Capybara.
Exotic Pets: Capybaras (‘Giant Hamsters’) Aren’t for Everyone
Capybara on Wikipedia.