Sea otters display sexual dimorphism as males are larger than females, measuring 1.2-1.5 m. in length and weighing up to 45 kg.
Sea otters utilize vertical undulates of the body to swim and can swim up to 9 kph or 6 mph underwater.
Sea otters inhabit marine neritic and oceanic habitats, spending most of their time foraging below the canopy and eating, resting, and grooming at the water’s surface.
Sea otters are one of several species of mammals that undergo delayed implantation that allows for birth under favorable conditions and produces varied gestation times.
Because sea otter’s don’t have insulating fat, their reddish brown fur consists of two layers and is the densest of all mammals with about 100,000 hairs/cm².
Starting at 2 months of age, sea otters are capable of diving to depths of at least 45 m., but prefer coastal waters up to 30 m. deep to find food easier.
Cat and opossum feces travel to storm drains via runoff and toilet disposal, eventually coming into contact with sea otters and infecting them with deadly apicomplexan protozoan parasites that cause encephalitis.
Sea otters communicate with 9 vocalizations and each otter has its own distinct scent that convey identity, age, and sex.
The maximum estimated lifespan of sea otters is 23 years in the wild.
Sea otters consume 20-25% of their body weight each day, eating 3-4 times a day, and tend to be specialized in their choice of prey.
Sea otters are polygynous, with males having multiple female partners throughout the year.
Because male sea otters hold the female’s head or nose with their jaws during copulation, many females have visible face scars.
Sea otters are diurnal with crepuscular peaks in foraging activity and spend 15-55% of their time foraging, depending on food availability.
Although twins occur in 2% of sea otters births, only one pup can be raised successfully.
Male sea otters don’t provide any care for their offspring while the females nurse, feed, protect, and groom the young for up to 6-8 months.
Female sea otters carry their pups on their bellies while they nurse, providing their young with 20-25% fat milk for up to 6 months.
Because sea otter fur is coveted for its density and insulating quality, sea otters were nearly hunted to extinction from the mid 1700’s to 1911 when the International Fur Seal Treaty was enacted.
Female sea otters usually give birth to a single pup about once a year at any time, though there are peaks of birth in May-June in the Aleutian Islands and in January-March in California.
Sea ice limits the sea otter’s northern range while the distribution of giant kelp forests limits its southern range.
Sea otters are found in two geographic regions on the Pacific Coast around Canada, the United States, and Mexico in North America and around Russia and Japan in Asia.
Sea otters are endangered due to large-scale population declines and hunting, but oil spills are their greatest anthropogenic threat.
Sea otters are the only carnivores with just 4 lower incisors.
Sea otters hunt on the sea floor using their sensitive whiskers to locate prey and their small, agile forepaws to capture the prey and pull it apart.
Great white sharks are one of the primary predators of sea otters, but the otters are also eaten by coyotes, bald eagles, and killer whales.
The Asian sea otter is the largest subspecies, followed by the northern sea otter, leaving the southern sea otter as the smallest.
Three subspecies of the sea otter are recognized with distinct geographical distributions and facial structures.
Sea otters are one of the few mammals that exhibit tool use, using rocks to break open prey and storing the rocks in the loose skin under their forearms.
When resting or sleeping, sea otters float on their backs and wrap themselves in kelp to keep from drifting.
Sea otters are a keystone species and are vital to the overall health and diversity of the kelp forest ecosystem by controlling herbivorous invertebrates.
Sea otters are social creatures and congregate in groups known as rafts or pods, though females tend to avoid males except when mating because males steal their food.