The Kodiak river otter (Lontra canadensis kodiacensis) is a sub species of the North American river otter and is found only on the Kodiak Archipelago. North American river otters range throughout much of Canada and the United States.
River otters are stocky, with short legs, webbed hind feet, a thick neck, a flattened head, small ears, and a muscular body. A strong tail that is more than one-third as long as the head and body helps propel them through the water when they swim. Adult river otters weigh 15 to 35 lbs. (6.8-15kg) and are 40 to 60 inches (102-152 cm) long. Females are usually about 25% smaller than males. An otter’s fur is black-brown in color on the legs and back fading to a slightly lighter shade on the belly. The chin and throat are gray. The fur consists of a dense undercoat and longer guard hairs. Several sets of strong whiskers sprout from beneath the nose.
A river otter is well adapted for living both on land and in the water. Its thick fur helps keep it warm when swimming in cold water, and its webbed hind feet, narrow body, and flattened head allow for streamlined movement through the water. An otter swims by paddling or vertically flexing its hindquarters and strong tail. It can swim 6 mph (9.7 km/hr) and even faster over short distances by “porpoising.” An otter can dive at least as deep as 60 ft. (18 m) and stay underwater for as long as eight minutes. On land, an otter can run up to 15 mph (24 km/hr).
River otters have well-developed senses of smell and hearing. Their vision on land is not good, but they may see better under water. An otter uses its whiskers to detect prey in murky or dark water, aid in navigation, and to avoid obstructions.
River otters can live in any water habitat, including ponds, marshes, lakes, rivers, estuaries and coastal areas. They can tolerate both cold and warm environments and can live at any elevation as long as the habitat provides an adequate food source. On Kodiak, river otters live in timbered habitat next to the coast. They often travel long distances overland between bodies of water and use the same trails year after year. While more common at sea level, river otters on Kodiak are sometimes found high in the mountains.
River otters reach sexual maturity at age two, and females produce one litter per year. In Alaska, otters breed in the spring, and breeding can take place in or out of the water. A female may give birth to as many as six pups, but two or three are more common. Due to delayed implantation of the fertilized egg in the uterine wall, pups may be born from late January to June after a gestation of nine to thirteen months.
Pups are born in a den, and at birth, they are toothless and blind. They open their eyes when they are seven weeks old, and at two months of age, they begin to leave the den and start to swim and eat solid food. Pups do not innately know how to swim but must be taught by their mother who sometimes has to force and even drag them into the water. Pups are weaned when they are five months old, but they stay with their mother until just before her next litter is born.
River otters are usually found in groups. Often these groups are related individuals, such as a mother and her pups, with or without an adult male. The female is normally the dominate member of such a group and will drive other animals away from the area around her den. Other groups may consist of siblings who have left their mother, a male and female otter, or a group of bachelor males. While otters live together in social units, they do not hunt together or share their catch with other members of their group. River otters may live for more than twenty years, but a lifespan of eight to nine years is more common.
In Alaska, river otters hunt on land and in fresh and salt water. They are opportunistic feeders and eat mussels, clams, sea urchins, snails, crabs, shrimp, octopi, fish, insects, birds, small mammals, and even plants. Otters normally eat their aquatic organisms on shore, and it is not unusual for us to find the remains of a river otter’s breakfast on our dock. If an otter catches a fish or other organism that is too big to eat in one meal, it eats what it can and abandons the rest of the food. River otters have a high metabolism and must eat often.
River otters spend half of their time sleeping. Both adults and pups are playful and like to slide on snow and mud. They wrestle, chase their tails, dunk each other in the water, and play with rocks and sticks. This playful behavior strengthens social bonds and aids pups in learning how to hunt.
River otters communicate with each other in a variety of ways. They use several vocalizations, including whistles, yelps, growls, and screams. When they are alarmed or upset, they emit a loud “hah” sound, and when two or more otters are together, they may mumble to each other as if in conversation. They chirp like a bird to express anxiety, and this sound is often heard when members of a group become separated from each other. Otters also communicate by body posturing and by touch. They use the scent produced by the glands at the base of their tail to mark their territories or to create scent trails to communicate where they have been.