The North American River Otter, a member of the weasel family, is the only River Otter found north of Mexico. Its luscious pelt, which is waterproof and allows the river otter to regulate its temperature, ranges from grey and white to brown and black.
Equally at home in the water and on land, the River Otter makes its home in a burrow near the water's edge, and can thrive in river, lake, swamp, or estuary ecosystems. These otters swim by propelling themselves with their powerful tails and flexing their long bodies. They also have webbed feet, water repellent fur to keep them dry and warm, and nostrils and ears that close in the water. In winter they remain active by using ice holes to surface and breathe. They can hold their breath underwater for up to eight minutes and dive to a depth of 60 feet!
On land, River Otters love to playfully slide down snow-covered, icy, or muddy hills—often ending with a splash in the water. Otter families of mother and children can be seen enjoying such fun, which also teaches survival skills.
Hunting and Feeding
River Otters hunt at night. These opportunists enjoy fish as a favorite food – they will travel far to take advantage of a salmon run, for example – but also eat amphibians, turtles, bird eggs, beetles, and small mammals.
The basic social group is a female and her offspring. Before and after breeding, male otters usually lead solitary lives. March through May, females retreat to these underground homes to deliver litters of two to four pups. At the tender age of seven weeks, these pups get their first introduction to the water—which consists of their mother pushing them in! When they reach eight to ten weeks, they begin exploring beyond the den and eating solid food. In late fall, the pups leave to establish their own territories.
Their Part in our Ecosystem
River Otters are an important part of a healthy, aquatic ecosystem. Finding them along a stream or river is a sign of clean water. Without river otters to regulate prey populations, an overabundance of these smaller animals can deplete the other animals and plants in the food web, disrupting the balance of the whole system.
Historically, River Otters were hunted for their pelts. Although there is no major threat from commercial harvesting today, illegal hunting can still affect local populations.
One of the main concerns is depletion of food source. Fish populations are at risk from climate change due to effects of sea-level rise. If these populations start to decrease in number or begin moving elsewhere due to climate change, there would be a knock-on effect on river otters.
River Otters are also threatened by habitat destruction – in particular their aquatic habitats, which are being affected by human contact. The root of most problems is water pollution, though the clearing of timber and other vegetation cover is also having an impact.
River Otters are often blamed for preying on wild game fish, and can occasionally cause severe problems in fish hatcheries and private ponds. They also den under houses, decks and other structures near water, and the smell of their droppings and food remains can be unpleasant.
The Washington Department of Fish & Wildlife has some great advice online for preventing conflicts.