Two names are commonly used in English for "Myocastor coypus". In France, nutria ("Myocastor coypus") was confirmed as a wild reservoir host of "F. hepatica". However, beavers' tails are flat and paddle-like, as opposed to the round tails of coypus. On the other hand, "Callistomys" (painted tree-rats) is the sister group to "Myocastor" (coypus). Newborn coypus nurse for seven to eight weeks, after which they leave their mothers. During cold winters, coypus often suffer frostbite on their tails, leading to infection or death. From Louisiana, coypus have spread across the Southern United States, wreaking havoc on marshland.