River otters are well suited to life in the water. They have streamlined bodies, fully webbed feet, and long, tapered tails that are thick at the base and flat on the bottom. Their ears and nose close when they go underwater. Dense, oily fur and heavy layers of body fat insulate them in the water. They have a keen sense of smell and prominent facial whiskers that are extremely sensitive to touch. Otters are dark brown with pale brown or gray bellies. The muzzle and throat are silvery. Males and females look alike, although males are larger. They are graceful, powerful swimmers and can remain submerged 3–4 minutes. On land, they travel with a loping gait. On snow or ice, they alternate loping with sliding.
Similar species: The American mink is smaller (total length up to 27 inches), almost entirely brown (with a white chin and irregular white spots on the throat, chest, and belly), with a tail that is not obviously thick at the base, not flat on the bottom, and not obviously tapering from the body toward the tip. The only other otter in North America is the endangered sea otter, which occurs in seawater only along the Pacific Coast and not in Missouri.
Total length: 35½ to 53 inches; weight: 10–30 pounds.
Statewide. Today, found in all major watersheds throughout the state.
Habitat and Conservation
River otters live in streams, rivers, and lakes usually bordered by forest. Burrows may be under large tree roots, beneath rocky ledges, under fallen trees, or below thickets. The burrows are usually former homes of muskrats, beavers, or woodchucks. Private and public landowner efforts to conserve streams, ponds, and lakes benefit otters.
Crayfish make up a large portion of an otter’s diet for most of the year, but during winter otters feed almost exclusively on fish. Other foods include mussels, frogs, turtles, aquatic insects, and other small animals. Otters use their whiskers to feel around underwater and find food.
A century ago, otters were nearly eliminated in Missouri because of unregulated harvest. Restoration efforts in the 1980s and early 1990s included the release of more than 800 otters in the state. Thanks to these efforts, and thanks to improvement of stream conditions, otters are once again found throughout most of Missouri.
Otters are mostly nocturnal and active all year. Social and generally living in family groups, they vocalize to each other through a variety of sounds including chirps, grunts, and snarls. Otters also communicate through scent at latrine sites. They regularly visit these sites to deposit droppings and secretions from their musk glands. Females whelp two to five young, usually in February or March. The young are weaned at 4 months of age but stay with their parents until the following spring. Otters are relatively long-lived. In captivity, some bred at 17 years and lived to 19 years of age.
Otters are playful, and people enjoy watching their antics.
Otter fur is thick, glossy, and luxurious, making it a valuable commodity.
While the fishing habits of otters do not endear them to fishermen, it must be realized that otters eat rough as well as game fish and take many other kinds of food besides fish, especially crayfish.
Research suggests that they have minimal impacts on fish populations in large streams, rivers, and lakes but may impact fish populations in small streams and ponds, and farmed fish.
If you are experiencing problems with otters, contact a wildlife professional for advice, assistance, regulations, or special conditions for handling these animals.
Otters help control aquatic prey populations. They often prey on types of animals that are most available.
They are eaten by bobcats, coyotes, and other large predators.
Otters and other animals that live in both aquatic and land environments play roles in both aquatic and land ecosystems.
Signs and Tracks
- 2½ inches long
- 5 toes.
- 2½–3 inches long
- 5 toes.
- Larger than mink tracks.
- Tail often leaves marks.
- Distance between track clusters is 18–30 inches (loping).
- The webbing between toes can leave a print in soft mud. Webbing is usually hard to see and is not distinctive as it is in beaver.
- The belly often drags in sand or snow.
- Otters create long slides 8 or more inches wide, in mud or snow, on sloped river banks.
- Otters also slide when traveling away from water, primarily on snow. In this case, tracks will be interspersed with long belly slides.
- Often travel in groups: bachelor males, and females with litters.
- Otters habitually roll around in grass, making flattened areas, but also collecting and clumping up vegetation into little mounds. These are commonly also latrine sites.
- Latrine sites distinctive. Dissolving scats often reveal fish scales, crayfish remains. Latrine sites are used repeatedly, often killing nearby vegetation.