Den entrances are often a foot or two beneath the water's surface, and the den entrance is often as much as two feet in diameter. The inner chamber of the den is above the waterline, and lined with grasses brought in to serve for bedding. This species is territorial and tolerant of others of its kind. Four or five colonies of nutria to the mile of levees or dikes indicates a high population as a family or colony territory is about 1,000 feet in length. Nutria do not remain underwater for long periods of time.
Research shows that they are capable of holding their breath while submerged for about five minutes.
A shy and retiring species, nutria are not usually seen unless there is a deliberate attempt to find them. Nutria burrow into banks of ponds and lakes, and these holes are usually larger and more destructive than muskrat burrows. General Nutria usually have a negative impact on other wildlife species. Because they are colonial in habitat, nutria often overharvest edible plants within their small range, resulting in the killing of the desirable plant species. Large populations of nutria definitely have a negative impact on the ability of the habitat to support both muskrats and waterfowl.