North American river otters are the only river otter that is found north of Mexico. This animal’s lovely waterproof pelt, which allows it to regulate its temperature, in the 1700s-1800s, a regular part of French fur trade, has meant this animal has been hunted for hundreds of years. Its fur ranges in color from white and gray to brown and black.
The North American otter inhabits much of the United States and Canada, from the Pacific to the Atlantic Coast, from the Gulf of Mexico to northern Alaska. Being aquatic in nature, this species is confined to places that have permanent water. This includes a wide range of habitats, from rivers, streams and creeks, to coastal waters, lakes and swamps.
For the majority of the year, this animal is most active during the period dusk until dawn, but in winter, it may more commonly be seen during the day. This species’ social structure is very variable, as some animals are solitary, while others live in family groups of an adult female with her offspring, or sometimes in large groups of just adult males. Groups typically travel and hunt together, and also use the same resting site and den. Dens are created in riverside burrows, under vegetation or rocks near water, in undercut banks or hollow trees, and sometimes in muskrat or beaver lodges. There is much overlap of individual home ranges, and though this animal is non-territorial, it uses scent-marking as an important means of communication. A range of vocalizations is also used to communicate, the most common sound amongst a group being a low frequency noise that sounds like chuckling, while loud snorts are often used for signaling potential danger.
The North American river otters are carnivores, they eat mainly aquatic animals such as amphibians, turtles, fish, crayfish, crabs, and other species of invertebrates. Birds and birds’ eggs, as well as small terrestrial mammals may also be eaten. Sometimes they eat aquatic plants.
North American otters are polygynous, with males often breeding with several females, probably ones whose home ranges overlap theirs. Breeding is from December to April: late winter or early in spring. Gestation is for two months, but young may be produced up to a year after breeding due to delayed implantation. Births take place from November to May, peaking in March and April. A female gives birth to 1 to 6 young in each litter, averaging 2 to 3. The otters have fur when they are born, but are otherwise helpless. Birthing and the raising of young takes place in a den near water. Pups will open their eyes when they are one month old and are weaned when about 3 months old, starting to leave their birth range from 6 months to the age of one year. They reach reproductive maturity at the age of 2 to 3 years.
River otters eat fish, and fish populations are threatened by climate change from rising sea levels. If fish numbers start to decrease or they move elsewhere as a result of climate change, this species would lose its major food source. They are also threatened by the destruction of their habitat. Human contact is influencing this otter’s aquatic habitats. Water quality is lowered, water is depleted, timber and other vegetation is cleared and becomes scarce. Most of these problems are due to water pollution. Historically, these animals were hunted for their coats. There is no significant threat today from commercial harvesting, but illegal hunting can affect local populations.
The Defenders of Wildlife resource, based on harvest reports, estimates the North American otter’s total population size to be over 100,000 individuals. Currently this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today remain stable.
North American river otter is important predator of fish and aquatic invertebrates.