Northern river otter, Common otter, River otter
The North American river otter (Lontra canadensis) is a semiaquatic mammal that lives along its waterways and coasts. It is the only river otter that is found north of Mexico. These animals live in burrows and like most predators, prey upon the most readily accessible species. They suffer greatly from habitat loss and are often captured for their fur. In the wild, they live only for 8-13 years but in captivity, their life expectancy can reach up to 25 years.
North American river otters have long whiskers that are used to detect prey in dark waters. They differ from the Eurasian otter by their longer necks, narrower visages, smaller space between the ears, and shorter tails. North American river otters have a transparent inner eyelid (called a nictitating membrane) to protect their eyes while swimming. Their fur ranges in color from white and gray to brown and black; it is very thick and water-repellent. Males and female river otters look alike but males are usually larger in size.
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 from 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 the 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 spring. Gestation is for 2 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, and timber and other vegetation are cleared and become 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 otters are important predators of fish and aquatic invertebrates.