River Otter
The largest aquatic weasel in Colorado, the river otter is a powerful river predator and keystone species.
About This Species
River otters are known for being playful, determined predators. In the late 19th and early 20th centuries, otter pelts were more valuable even than beaver, which was a leading factor in their extirpation from the state. In the 70s, CPW began restoring the species to the state's waterways.
River otters are a top river predator, helping control the populations of species they prey on. They also play a critical role in indicating river health: if the population is increasing it indicates the ecosystem is healthy.
Conservation
State Threatened Species
The river otter's status in Colorado was changed from endangered to threatened after CPW's management efforts successfully increased the animal's population.
Read the river otter conservation plan
Hydrology
- Maintain natural regime to extent possible.
- Protect instream and seasonal flow regimes.
- Enhance and/or protect stream and habitat connectivity.
Vegetation
- Maintain or recreate conditions favoring healthy riparian vegetation.
- Encourage new recruitment of trees.
- Manage for age diversity.
Land Use/Other
- Enhance and/or protect bank structure.
- Enhance and/or protect flood plain.
- Enhance and/or protect good water quality.
- Protect potential upland denning sites from flooding.
- Manage for prey base (e.g., fish).
Conservation
- Monitor and control commercial harvest to maintain desirable population numbers.
- Form and maintain partnerships across jurisdictional boundaries to protect connectivity and long stream reaches.
Conservation
Bringing the River Otter Back to Colorado
Colorado is among 21 states making a concerted effort to reintroduce and foster River Otter populations. Colorado Parks and Wildlife has successfully reintroduced river otters to the Western Slope. Because our river otter populations are doing so well, our efforts are now dedicated to monitoring them. Otters are notoriously difficult to keep tabs on, but our teams are involved in intensive efforts to learn more about their populations. In order to collect data on the otters and their whereabouts, our teams of specialists have to go where the otters are: to the river. We take intensive river trips in the spring and summer to learn all we can about these playful river dwellers. There’s currently no need to intervene, but we are dedicated to maintaining our knowledge base and making proactive plans.
More Information:
Physical Characteristics
Size
The river otter is the longest of our weasels, ranging from 3 to 4 1/2 feet, of which the powerful, cylindrical tail (which thickens toward the base) comprises about one-third. The otter is about twice as long and five times as heavy as mink, and is the only other aquatic carnivore in the Rockies.
Swimming
Webbed toes and water-resistant fur suit the animal to a life spent largely in water. Otters sometimes paddle, but the force for swimming comes mostly from eel-like movements of the body and tail.
Color
Otters are rich brown in color, with silvery brown beneath.
Range
Once otters probably occurred in major streams statewide in Colorado, although they apparently have never been abundant. With settlement, subsequent water pollution and control of streamflows, otters disappeared from the state by the early part of the 20th century. In the 1970s, however, the Colorado Parks and Wildlife began to restore populations to several drainages, including the Upper Colorado, the Dolores and the upper South Platte rivers.
Habitat
Otters live in riparian habitat. Otters usually live in bank dens abandoned by beavers. They are active mostly at dawn and dusk, and appear to spend large amounts of time just playing—sliding on ice, snow and mud, and swimming gracefully for no apparent reason beyond swimming.
Diet
Their diet consists of aquatic animals like crayfish, frogs, fish, young muskrats and beavers are favored foods.
Reproduction
Otters breed in spring. Embryo implantation is delayed until the following winter, and up to four young are born in early spring. While the female is nursing one litter, mating occurs again.
Threats to Species
- Climate Change and Severe Weather
- Residential and Commercial Development
- Energy Development and Land Use