By Karen Anderson, Master Naturalist/ACLT Guest Blogger
The North American river otter (Lontra canadensis) is one of 13 species of otters worldwide and is the one species that is found in our area. While some are lucky to actually spot an otter or group of otters, the most likely way you will know they are around is by finding their signs – tracks, slides, or their latrine areas.
Otters are found in most aquatic habitats around the world, except for Australia, Antarctica, and the northern parts of the Arctic.
North American river otters are found throughout most of the United States and Canada, except for arid portions of the southwest. As a semi-aquatic mammal, they are found along most types of waterways and coasts – including fresh, brackish, and marine water. In our area, they are found in rivers and streams, and along the Chesapeake Bay coast and make their dens in embankments along the waterways.
Before European settlers came to North American, river otters were common throughout the continent. Over harvesting for their fur, loss of their habitats by filling of wetlands, along with pollution caused many populations to disappear. By the 1970s, State wildlife agencies had concerns about otter populations and began reintroduction programs. Since 1976 over 4,000 otters have been reintroduced among 21 states (IUCN website). With improved water quality, and a decrease in the loss of wetlands, otters have rebounded in many states. Today, oil spills, runoff from mining, and continued land development can still affect otters in localized areas.
Although otters are present here in Calvert County and on ACLT property, you may not see them often as they tend to be shy of people and are most active from dusk into the night. In fact, usually the way people know they are around is by spotting their scat or latrine areas which may be on a dock, a particular rock, or other prominent area. These communal latrines are used by a family group, in part, to communicate with other otters.
You may also spot their tracks in snow or on a sandy beach or muddy bank, or find their slides – which might be easy to spot after a snow. Another way you might know an otter has been around is by their strong musky smell – they use the scent glands near their tails to advertise that they have been at a particular site within their home range by rubbing on vegetation. Otters will also communicate with each other using squeaks, whistles, twitters, chirps, and growls.
Built for aquatic life, otters have dense fur which they need to keep groomed to maintain water repellency. Otters have long tapered tail which helps propel them in water; small ears, and vision adapted for underwater (so near-sighted out of water), along with short legs and fully webbed feet bearing non-retractable claws. Adult otters weigh from 10 to 33 pounds and are about 2.5 to 5 feet long. Females are roughly a third the size of males.
Otters feed opportunistically but consume primarily fish. They also eat crustaceans, mollusks, amphibians, insects, and even occasionally birds. Otters have a high metabolism and feed throughout their active hours. Being at the top of the aquatic food chain, contaminants such as heavy metals and other pollutants can bioaccumulate in the food they consume and may affect their health.
River otters form family groups and the young stay with their mother for about eight months after they are born, typically in April-May; they leave when the mother gives birth to another litter. Like most mammals, young otters spend time playing with each other learning skills they will need when they venture out on their own. Some studies on river otters indicate that they mate for life, while other studies seem to indicate that the male only stays with the female for a few months during the breeding season.
Otters have been spotted only rarely on one of ACLT’s trail cameras (see video below).
If you want to see live river otters, you could visit the Calvert Marine Museum in Solomons, the Baltimore Zoo, or National Zoo – check their websites for current visiting protocols.
You may also enjoy watching otter videos on the Smithsonian Environmental Research Center’s Facebook page.
Links with additional otter information and otter cams: