Sea otters are adorable, furry seafarers found in coastal regions of the North Pacific Ocean. Although they are a popular animal with visitors to zoos and wildlife parks, not much is known about these aquatic mammals. One of the most common questions asked is what sea otters eat. Read on to find out and learn more about these curious creatures.
Sea Otter Stats
Sea otters are carnivorous aquatic mammals belonging to the same family as weasels, mink and wolverines. They have a large chest, a short muzzle and webbed hind feet. They are covered in thick fur and they use their dextrous front paws to hunt. Sea otters also make use of their front paws to hold food while they eat and hold their pups.
There are 2 subspecies of sea otter: Alaskan and Californian otters. Alaskan sea otters are larger than their Californian cousins but most other characteristics are the same.
Adults Alaskan sea otters can weigh up to 39kg (86lbs), whereas Californian sea otters weigh 10-15kg (22 – 33lbs) less, depending on gender.
Differences between Sea Otters and River Otters
People often mistake sea otters and river otters for one another. They are both part of the same family, but there are easy ways to tell them apart.
River otters are found in both freshwater and saltwater, whereas sea otters live in the ocean and hardly ever venture on land. Freshwater otters build dens for shelter and to raise their young. Sea otters float on their backs to rest and mothers will carry their young on their stomachs. To prevent themselves from flowing away, sea otters will ‘hold hands’, linking their front paws together while they sleep.
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Sea Otter Habitat
Sea otters are found in coastal regions in the eastern North Pacific. Alaskan sea otters live in Arctic waters around Alaska, while California sea otters prefer the warmer water off the coast of central California.
The arctic waters around Alaska are cold. Nevertheless, they support a huge marine ecosystem, especially for invertebrates and crustaceans sea otters eat. The warmer waters along the California coastline have a wider array of fish species.
Rising sea temperatures is causing a slow but noticeable shift in the availability of prey animals, which is having an adverse effect on sea otter numbers.
Sea Otter Diet & Hunting Habits
The diet of sea otters is unusual in that they must eat a large quantity of food compared with their body size. They have a higher metabolic rate than many other mammals, meaning they burn calories faster in order to produce energy.
An adult sea otter can consume up to 10kg (22lbs) of food every day. Sea otters like to eat a varied diet of crabs, clams, mussels, sea urchins, fish and small octopus. They have retractable claws on their forefeet that allow them to easily open shells and grasps slippery fish.
While river otters can dive 50-60 feet (15-18m), sea otters are capable of diving to depths of 100-200 feet (30-60m) and can stay submerged for almost 10 minutes at a time.
Sea otters typically dive between 40 and 80 feet (12-24m) to hunt for food, using their strong webbed hind feet to propel them through the water. They have very sensitive whiskers, which can detect movement and changes in water currents.
Once they spot their prey, sea otters use their dextrous front paws to grasp it firmly. Sea otters are intelligent animals and have been observed using rocks to remove molluscs from larger rocks. They also use rocks to crack open prey such as mussels and crab. How they do it is peculiar as they lay their food on their stomach and bang a rock against it.
Pups observe their mothers doing this and will practice with empty shells until they are weaned and able to hunt for themselves.
Breeding & Social Behaviour
Female sea otters do not reach sexual maturity until 4 years of age, while males do not actively breed until at least 6 years of age. Sea otters live a surprisingly long time for a small mammal, but not so long considering they live in such a rich ecosystem. The average lifespan of a wild sea otter is 12-15 years.
There is no set breeding season, with adults mating at any time during the year. Experts believe that female sea otters experience delayed implantation, which allows the pups to be born at a safer time of the year when the temperatures are warmer and food is likely to be easier to find.
Pregnancy is between 6 to 9 months depending on the subspecies. When the pups are born, they are covered in a layer of thick fur. The mother will float on her back and support her young on her stomach. When she goes off to hunt, she will often leave her pups wrapped in kelp on the water surface to prevent them from floating away.
Most pups are weaned off their mother’s milk by the age of 8 months, but will remain close to their mothers. Sea otters are social animals and are often seen in small groups called rafts. They can be quite vocal, especially where food is concerned.
Males leave their mothers after weaning to join male only groups, but each male will establish his own small territory. Females and their young form groups together and they will roam freely between male territories.
Threats for Sea Otters
Sea otters once numbered in tens of thousands, but centuries of hunting saw a sharp decline. The population of sea otters today occupies less than 20% of their original range between Alaska and California.
The biggest threat faced by sea otters today is entanglement in commercial fishing nets. They are also at risk from oil spills, predation from sharks and decline in food availability.
Populations have been increasing steadily since 1980. However, their numbers are still below 3000 individuals and in 2017 the population count began to decline. Between 2017 and 2020 the population of sea otters in the North Pacific fell by an estimated 400 individuals. There are several possibilities for this decline, including an increase in shark predation, disease and toxic algae blooms caused by the changing climate.
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