The biggest weasel species are the charismatic otters. Otters are semi-aquatic, in contrast to other weasels. Their svelte bodies come in sizes between 2 and 5.9 feet. In rivers on five continents, thirteen otter species can be found sliding down riverbanks, juggling boulders, and floating on their backs.
Australia and Antarctica are the only two locations devoid of indigenous otters. On the IUCN Red List of Threatened Species, all otter species are present, and only one is designated as “least concern.”
They are excellent divers and swimmers due to their long, streamlined bodies. Their back feet serve as rudders to steer while their long, slightly flattened tails move sideways to propel them through the water. Otters have rounder noses with whiskers that help them identify prey and predators as well as changes in the water current. Otters have the ability to cover their ears and noses when swimming underwater. Otters may remain underwater for five to eight minutes, depending on the species. They utilize less oxygen when swimming and their pulse rates slow down.
Otters have two layers of fur: a dense undercoat that traps air and a topcoat of long guard hairs that are waterproof. Otters come in a variety of colors of brown, with a significantly darker dorsal (back) surface and a much lighter ventral (underside), though their coloration varies. Otters spend a lot of time grooming to keep their fur in good condition because if it isn’t, it could interfere with their ability to find food and stay warm.
The sea otter inhabits kelp forests and estuaries in Monterey Bay. The sea otter is a keystone species, which means that the health of sea otters is a reliable indicator of the health of other species and ecosystems nearby. It consumes sea urchins and other creatures that feed on giant kelp in the kelp forest. Kelp forests can survive and support a diverse range of plants and animals when sea otters are present to help reduce the urchin population.
Similar to this, in estuaries, otters consume crabs to maintain the condition of the eelgrass, allowing the sea slug population to increase. The algae that would otherwise cover and choke the eelgrass that fish depend on for food and shelter is subsequently consumed by these sea slugs.
The home range of a North American river otter can be up to 30 square miles (78 square kilometers), but the normal territory is between 3 and 15 square miles (4.8 and 24 square kilometers). Throughout the mating and rearing season, that home range significantly decreases. River otters are known for their lively demeanor and tend to live alone or in pairs, but they can frequently interact in groups.
There is proof that river otters’ playtime activities improve their hunting skills, social relationships, and territorial scent marking. They urinate, defecate, scratch, and rub their scent glands on rocks and trees to scent mark their area throughout the day.
After a gestation period of two months for smaller species and five months for bigger species, female otters give birth to one to five pups, usually two young. Usually, the mother gives birth to her offspring in a den. For smaller species, babies weigh 4.5 ounces, whereas larger species, such sea otters, can weigh up to 5 pounds. After giving birth, the woman will frequently eject the father.
Only in a few species does the father come back to assist in raising the pups, the young. Depending on the species, otters achieve sexual maturity at 2 to 5 years of age. Sea otters have a special breeding process because of their marine habitat. When these puppies are born, they have open eyes and a fur coat that helps them float in the water. Until the child is old enough to swim independently, the mother will often cradle the infant on her stomach when it is two months old.
Depending on their habitat, otters have a variety of natural predators. In the meantime, big cats, anacondas, and caimans are dangerous to the young of enormous otters. Depending on their area, otters may also face various dangers. For instance, fishing-related risks like being tangled in fishing gear and habitat damage pose a threat to river otters. Because of their fur, California sea otters were hunted to almost complete extinction a century ago.
River otters mostly consume aquatic animals like fish, frogs, crayfish, turtles, insects, and even small mammals. While otters typically graze in water, they are equally at home on land. They may travel up to 18 miles (29 kilometers) in search of food at times. Otters hunt alone or in pairs.
The extremely rapid metabolism of North American river otters, which also necessitates that they consume a lot during the day, gives them an endless supply of energy. They consume a variety of fish species and cooked meat at the Smithsonian National Zoo. For diversity and enrichment, they are also given live fish, crickets, mice, carrots, hard-boiled eggs, clams, crayfish, dry kibble, and hard-boiled eggs.
A normal North American river otter, assuming it survives its first year of life, will live to be 12 years old, with some living even longer. The oldest river otter ever found alive was 27 years old.