River otters were once found on all of the major waterways in North America. Because of the value of the pelts, however, hundreds of thousands of them were trapped, and by 1900 they were gone from many of the areas where they had once lived.
More recently, they have been reintroduced into many habitats, with the hope that they will eventually breed and expand into other areas. River otters are semi-aquatic, carnivorous mammals. They live in burrows, in holes in riverbanks, under large rocks, and in hollow logs.
In New England, river otters can be found in local waterways, such as the Kiekamuit, a river that crosses the Massachusetts/ Rhode Island border.
The river otter is a long, sleek, muscular animal. The typical adult male measures 3 to 4 feet in length and weighs 15 to 25 pounds. Females are somewhat smaller. They normally live for 10-20 years.
The water-repellent fur is short and ranges from brown to brownish gray above and is lighter beneath.
River otters have webbed feet and a streamlined body, which makes them very efficient swimmers. Its long, heavy, flat tail, which is used as a rudder in the water, is 12 to 18 inches long.
The ears and nose close when the otter is submerged, and a third eyelid, called the nictitating membrane, protects its eyes while allowing it to see while underwater.
Food and Diet
Their diet consists of fish, mollusks, frogs, eggs, snakes, birds, and small mammals.
In clear water, otters depend on their vision to identify food, but in turbid water they use their highly sensitive whiskers.
Fishermen have sometimes blamed otters for taking gamefish, but actually they’re much more likely to feed on slow-moving species and groundfish.
Otters usually live in dens that the burrow into the bank of a stream, but sometimes they simply take over abandoned beaver lodges or muskrat houses.
Mating generally takes place in March or April in temperate regions, but it can vary greatly. Through a phenomenon called delayed implantation, the fertilized egg floats free in the uterus for about nine months, then attaches itself to the uterine wall and begins developing.
The gestation period from that time is about 63 days. The typical litter of 2 to 4 is born in early spring. Newborn otters are blind and helpless. Their eyes don’t open until they’re about three weeks old.
By the time they’re two months old, young otters are ready to leave the den and enter the water. Mothers spend several months teaching them how to swim and catch their food.
At about six months of age, the young otters can pretty well take care of themselves, but they often stay with the mother until they’re 12 or 13 months old, when a new litter is born.
Because of their size and swimming ability, otters have few natural enemies when they’re in the water, but young otters are vulnerable to various types of predators on land. The river otter lives to about 15 years in the wild and up to 25 years in captivity.
The Playful Otter
Otters are among the most playful of animals, even when they’re grown up. An otter’s playful behavior is a means to strengthen social bonds and practice hunting techniques. They slide on mud banks, rocks, snow, and ice.
They enjoy chasing one another around and wrestling. Like porpoises, they also seem to enjoy diving and swimming just for the fun of it.
Sometimes, otters appear to stage their own fishing competitions, taking turns catching prey and releasing it.