Sea Otter

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.

Description

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.

Subspecies

The sea otter has three distinct subspecies, spread over diverse geographical locations.

• Asian sea otter – Occupying a large area from northern Japan’s Kuril Islands to Commander Islands of Russia
• Northern sea otter – Found between Aleutian Islands of Alaska, to Oregon
• Southern sea otter – Endemic to the central and southern parts of California

Range and Distribution

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.

Habitat

They occupy coastal marine regions, including coastal wetlands, rocky shores, and sea bottoms. Otters prefer places with nearby forests of giant kelp.

Diet

An otter’s diet consists of chitons, coast mussels, limpets, sea urchins, sea stars, and purple-hinged rock scallops. They also eat crabs, octopus, squid, and fish.

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.

Lifespan

A sea otter lives for 15 – 20 years on average, reaching a maximum of 23 years.

Behavior

• These otters tend to rest in groups called pods or rafts, where they float on their backs. To prevent themselves from drifting off, they have been seen holding hands or latching onto a patch of kelp.
• They are diurnal, foraging for food in the morning, resting during mid-day, and finally foraging once more before sunset. Some otters, notably females with pups, will forage a 3^rd time at night.
• Otters groom themselves periodically, including cleaning their fur, untangling their knots, drying their coat by removing water and blowing air, and eliminating loose ends. Occasionally while eating, they will roll over in the water to remove accumulated food scraps.
• Sea otters make several different types of sounds, including distress screams and contented coos, as well as growls, snarls, whistles, and whines.

Predators

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.

Adaptations

• Sea otters have a small pouch of skin under each foreleg that extends across their chests. This pouch is used to store food and carry tools, like rocks, which help open the hard shells of animals like abalones and urchins.
• The thick fur of a sea otter plays a vital role for its survival, including keeping it warm in cold waters and helping it stay buoyant.
• Their lung capacity is 2.5 times greater than most of its land-based brethren, allowing it to remain submerged for long periods.
• Otters have long, and sensitive whiskers called vibrissae, which help them locate prey quickly.
• With the help of its tail, powerful hind legs, and webbed feet, the sea otter can swim exceptionally well, and can even propel underwater with ease.

Mating and Reproduction

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.

Life Cycle

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.

Conservation Status

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.

Interesting Facts

• Sea otters have become the face of marine conservation, as the image of the expressive face of a sea otter getting submerged in oil brought immense sympathy worldwide.
• They do well in captivity, with the Seattle Aquarium being the first to raise sea otters from conception to adulthood in the 1980s. Over 40 public aquariums and zoos worldwide have also reared these sea mammals.
• Like the Ainu in the Kuril Islands and the Aleut in the Aleutian Islands, several indigenous cultures had a close relationship with the otter both materially and culturally. This relationship has declined due to commercial exploitation of the sea otter. 
• There are several differences between river and sea otters, for instance the sea otter is 2-3 times larger and have more fluffy fur compared to sleek fur of their freshwater counterparts.