- A-Z Animals
The sea otter is a marine mammal with the unique characteristic of coming without a blubber, unlike its other counterparts at sea, relying on its extremely thick fur to survive in the sea. While capable of moving on land, most of its activities like eating, resting, mating, and even giving birth occur in the ocean.
They are a keystone species, i.e., the ecosystem in which they live heavily depends on them. Contrastingly, the sea otter has suffered dramatically due to environmental damage and is endangered as a result.
Length: Male: 3 ft 11 in – 4 ft 11 in (1.2-1.5 m) Female: 3 ft 3 in – 4 ft 7 in (1.0-1.4 m)
Weight: Male: 49-99 lb (22-45 kg) Female: 31-73 lb (14-33 kg)
Fur: The sea otter’s fur is very dense, consisting of almost 150,000 strands of hair. There are two types of fur – long, waterproof guard hairs and the short underfur; the guard hairs help to keep the underfur dry. Air is trapped in a compartment between the coat and the skin, heating the body. This keeps cold water away from the skin, limiting heat loss. The fur is regularly groomed by the otters, as its effectiveness depends on how clean it is.
Teeth: They have 32 teeth, all flat and round, helping them crushing food well than cutting it.
Tail: Their tails are muscular, short, stout, and a little flattened.
Body and Coloration: Its front paws are short with retractable claws and tough pads on the palms helping it grip slippery prey. The hind feet are long, flat, and fully webbed with an elongated fifth digit on each foot.
The color of its fur generally is a deep brown with silver-gray speckles. Other colors like yellow, grayish-brown, or black have been observed in some cases. The head, throat, and chest are lighter than the rest of the body.
The sea otter has three distinct subspecies, spread over diverse geographical locations.
Sea otters are found in parts of the Russian east coast, Alaska, British Columbia, Washington, and California. There are recent reports of them being found in Mexico and Japan.
They occupy coastal marine regions, including coastal wetlands, rocky shores, and sea bottoms. Otters prefer places with nearby forests of giant kelp.
Individual otters have been noted to have preferences for certain types of food. For instance, one otter may prefer to eat urchins while another likes crabs.
A sea otter lives for 15 – 20 years on average, reaching a maximum of 23 years.
In the water, great white sharks target sea otters for food while on land, coyotes may attack trapped otters. Bald eagles have been known to carry off pups.
They are polygynous, i.e., males have multiple female partners. Sometimes, a female in heat and her mate, however, will bond temporarily.
Sexual intercourse takes place in the water. For the females, mating is often violent and non-consensual as the male commonly bites her muzzle, leaving scars on her nose. In some cases, the males would even hold their partner’s head underwater.
After a gestation period ranging from 4-12 months, a single pup weighing 3-5 lbs is born. Twins are rare, with only a 2% chance, and even in those cases, generally, only one pup survives. Pups are usually born with their eyes open, teeth emerging, and dense fur that allows them to float in water, similar to a cork though they cannot to dive. The adult fur replaces the baby fur in about 13 weeks.
After nursing the pup for a few months, the mother begins to offer it small pieces of prey. The pup will practice swimming and diving for several weeks under the supervision of its mother before it can reach the seafloor. The juveniles attain independence at 6-8 months. Their mortality rates tend to be high, with chances of survival improving based on how experienced the mother is in tending the kids.
Males become sexually mature at 5 years of age but begin mating much later. Juvenile females mature sexually a lot quicker at 3-4 years.
Female otters are highly devoted to young otters, even caring for orphaned pups. Mothers give their infants almost constant attention, cradling them on their chest away from the cold water, grooming their fur, and when out foraging, they will often wrap the pup in kelp to keep them from floating away. Mothers have been known to mourn by carrying their pups for days after they have passed on.
The IUCN currently lists the sea otter as “Endangered” or “EN”. The main threat to these mammals are oil spills, which clog their fur, causing them to die of hypothermia. Other issues plaguing them include parasites and infectious diseases, especially those transmitted by cats and opossums.
Until the turn of the 20th century, sea otters were regularly hunted for their fur, making them nearly extinct, with approximately 2000 individuals remaining. After a ban was imposed on fur-bearing sea mammals in 1911, the population began to rise again. However, the Exxon Valdez oil spill of 1989 gave a massive blow to the resurgent population, killing nearly 5000 individuals.