North American River Otters
Range & Habitat
The North American River Otter can be found in Canada and the United States. Otters can live in both marine and freshwater environments. Found in rivers, lakes, marshes and other inland waterways; otters live in dens underground. They prefer tributaries of major, unpolluted drainages where there is minimal human disturbance. Log jams and submerged trees provide resting and feeding habitat. Often dens are in abandoned beaver lodges and bank dens. Aquatic habitat must provide an abundant amount of prey, such as slow-moving fish.
River Otters are of the Mustelidae Family, along with wolverines, weasels, skunks, ferrets and sables. There are more than a dozen different species of otter, only two of which live in North America (River and Sea Otters). Otters are highly adapted for swimming, possessing a long, tapered body with sleek, close, tight fur. Its small head widens to the neck and shoulders. Their teeth are like those of other carnivores - adapted for grasping, grinding, shearing and crushing. Their large feet are webbed. The tail is flattened and is well muscled; and acts as a rudder as well as a prop when on its hind legs. They have specially adapted lenses in their eyes to accommodate underwater distortions, so while sight is not their strongest sense, they can see equally well on land as under water. Ears and nostrils can be closed when animal is submerged. They have well-developed senses of smell and hearing. They spend half of their lives sleeping.
The animals can discharge a strong, disagreeable scent from a pair of anal glands when threatened or disturbed. Otters are generally nocturnal or crepuscular (dawn/dusk), although diurnal activity is not uncommon in undisturbed areas. River otters are often seen in family groups in the summer and early fall. Communication consists of whistles, snorts, chirps and chuckles above and below the water. While not officially endangered, otters have suffered badly from habitat destruction, the use of pesticides, water pollution (bad water quality) and excessive trapping for their fur.
Reproduction & Growth
River otters are generally solitary except for transient pairings at breeding season. Otters usually reach sexual maturity at two years of age. Breeding occurs in early spring following the birth of a litter. They are induced ovulators - meaning that they must mate repeatedly and for a long period of time to ensure the release of an egg from the ovary. The river otter's reproductive cycle involves delayed implantation of the fertilized egg, an arrested period of development and embryo growth. This process is not yet fully understood. Delayed implantation results in a gestation period of 290-380 days. Actual embryonic development is thought to be about two months. One to five (usually two) infants are born with the female caring for the litter. Newborn pups are silky black in color, blind, toothless, helpless and weigh only 4-6 ounces. They grow rapidly and emerge from the den at two months of age when they start eating solid food. Maximum length is reached at three to four years of age. An adult's weight ranges from 11-33 pounds.
They have the potential to live, in zoos, 23 years; though the average life expectancy is 10-15. The longer life expectancy is because these otters live in a protected environment. It is free of predators and threats and they receive nutritional balanced diets, veterinary care and mental and physical stimulation with a variety of enrichment and management programs.
In the Wild: Many species of fish, freshwater mussels, frogs, or water birds, rodents, crayfish, snakes as well as aquatic bulbs and roots and blueberries! Otters compete with man and other animals for fish, but prefers non-game fish. In the Zoo: They currently eat beef, poultry, fish, eggs and omnivore biscuits.