Description: It is a medium- to large-sized semi-aquatic rodent highly specialized for life in wetlands and calm freshwater environments. Ondatra zibethicus possesses a sturdy body, short neck, relatively small head, and a long laterally flattened tail that functions as an effective rudder while swimming. Its dense, waterproof fur ranges from dark brown to reddish-brown and provides excellent insulation against cold temperatures. The hind feet are adapted for aquatic locomotion, while the lips can close behind the incisors, allowing the animal to cut underwater vegetation without taking in water. Beyond its swimming abilities, this species is notable for its capacity to modify habitats through the construction of lodges and burrow systems, making it an important ecological engineer in many wetland ecosystems.
Geographic Distribution: Native to North America, this species occurs across most of Canada, large portions of the United States, and northern Mexico. Owing to its historical importance in the fur trade, it was introduced into several regions of Europe, Asia, and South America, where self-sustaining wild populations became established in some areas. Today it occupies a broad range of temperate and cold regions, remaining closely associated with freshwater habitats. In certain introduced regions, populations have reached high densities and may significantly influence local ecosystems and vegetation communities.
Habitat: It primarily inhabits marshes, swamps, ponds, lakes, slow-moving rivers, irrigation canals, and vegetated wetlands. Areas with dense emergent aquatic vegetation are particularly important because they provide food, shelter, and construction materials. Individuals may excavate burrows into banks or build characteristic vegetation lodges that serve as resting, breeding, and refuge sites. The species is strongly dependent on the availability of permanent or semi-permanent aquatic habitats and is often considered an indicator of healthy wetland environments.
Diet: A predominantly herbivorous mammal, it feeds mainly on stems, roots, rhizomes, leaves, and shoots of aquatic and shoreline plants. Cattails, reeds, rushes, and other emergent wetland vegetation constitute important dietary components. Although plant material forms the bulk of its diet, it may occasionally consume mollusks, crustaceans, aquatic insects, small fish, or carrion. Seasonal changes in food availability strongly influence dietary composition, and the species demonstrates considerable flexibility in exploiting locally abundant resources.
Behavior: Activity is generally crepuscular and nocturnal, although daytime activity may occur in areas with minimal disturbance. It is an excellent swimmer and diver, capable of remaining underwater for several minutes while foraging or avoiding predators. Individuals frequently use established aquatic pathways and maintain intricate networks of tunnels and shelters. While some degree of tolerance may occur among neighboring animals in productive habitats, territorial behavior is also common, particularly around valuable resources. Communication involves scent marking, vocalizations, and visual displays.
Reproduction: This species has a high reproductive potential, a characteristic that contributes significantly to population growth. Breeding usually occurs from spring through early autumn across much of its range. Following a gestation period of about one month, females produce litters commonly containing four to eight young, although litter size may vary. Newborns are relatively undeveloped and depend entirely on maternal care during their earliest weeks. Rapid growth enables juveniles to become independent quickly, and many individuals reach sexual maturity within their first year of life.
Conservation Status: Due to its extensive distribution, large population size, and ability to occupy a wide range of aquatic habitats, the species is classified as Least Concern (LC) by the International Union for Conservation of Nature. Although local populations may be affected by wetland degradation, pollution, disease outbreaks, or management programs, the species remains abundant and stable across most of its global range.
Author of this compilation: EcoRegistros – 25/06/2026