Capybara
The capybara ("Hydrochoerus hydrochaeris") is a mammal native to South America. It is the largest living rodent in the world. Also called chigüire, chigüiro (in Colombia and Venezuela) and carpincho, it is a member of the genus "Hydrochoerus", of which the only other extant member is the lesser capybara ("Hydrochoerus isthmius"). Its close relatives include guinea pigs and rock cavies, and it is more distantly related to the agouti, the chinchilla, and the coypu. The capybara inhabits savannas and dense forests and lives near bodies of water. It is a highly social species and can be found in groups as large as 100 individuals, but usually lives in groups of 10–20 individuals. The capybara is not a threatened species but it is hunted for its meat and hide and also for grease from its thick fatty skin, which is used in the pharmaceutical trade.
Beaver
The beaver (genus Castor) is a large, primarily nocturnal, semiaquatic rodent. "Castor" includes two extant species, the North American beaver ("Castor canadensis") (native to North America) and Eurasian beaver ("Castor fiber") (Eurasia). Beavers are known for building dams, canals, and lodges (homes). They are the second-largest rodent in the world (after the capybara). Their colonies create one or more dams to provide still, deep water to protect against predators, and to float food and building material. The North American beaver population was once more than 60 million, but as of 1988 was 6–12 million. This population decline is the result of extensive hunting for fur, for glands used as medicine and perfume, and because the beavers' harvesting of trees and flooding of waterways may interfere with other land uses.