Alaska Marine Mammals: Sea Otters

Marine Mammals: Sea Otters

Alaska's State Flower is the "Forget-Me-Not. Forget me not flowers are very fragrant in the evening and night time, though there is little or no scent in the daytime. They can be annual or perennial plants. Their seeds are found in small, tulip shaped pods along the stem to the flower.

The sea otter is the largest member of the weasel family and the smallest marine mammal. Ninety percent of the world’s sea otters live in coastal Alaska. Sea otters were hunted nearly to extinction in the late 1700s and 1800s through commercial harvest for their luxurious furs. Once commercial harvest ceased, sea otter numbers rebounded and they re-colonized much of their former range.

Sea otter numbers have declined in southwestern Alaska over the past 20 years. Once containing more than half of the world’s sea otters, this population segment, which ranges from Kodiak Island through the western Aleutian Islands, has undergone an overall population decline of at least 55–67 percent since the mid-1980s. In 2005, the U.S. Fish and Wildlife Service listed this distinct population segment as Threatened under the Endangered Species Act

Sea otters teeth are adapted for crushing hard shelled invertebrates such as clams, urchins, and crabs. The skeletal structure of the sea otter is loosely articulated and lacks a clavicle which allows for increased flexibility in swimming and grooming. The fore limbs are used primarily for grooming and foraging rather than swimming. The hind feet are flattened and flipper-like with an extension of the fifth digit which enables the animal to more efficiently swim on it’s back on the surface oft he water.

Sea otters do not have a blubber layer as other marine mammals do, instead they depend upon a dense, water-resistant fur to provide insulation against cold. Sea otter fur is very dense and has a greater number of hair follicles per inch than any other mammal. Adult sea otters can reach lengths of up to 6feet (1.8 m) but average about 4.5 feet(1.4 m). Adult male otters weigh from70 - 90 pounds (32-41 kg) with some males reaching up to 100 pounds (46 kg).Adult female otters average 40 - 60pounds (18-27 kg).

Sea otters compensate for having a small body size and no blubber layer by having an increased metabolism which helps them keep warm in the cold water. Sea otters in captivity will consume up to 25% of their body weight per day.

Sea otters dive to gather food from the ocean floor in relatively shallow water in areas with both rocky substrates and soft bottom sediments. A loose pouch of skin at the axilla (arm pit) of each forelimb is used to store and transport food to the surface. Sea otters eat a wide variety of benthic invertebrates including: clams, crabs, sea urchins, snails, octopus, and occasionally fish and sea birds. Diving depth of sea otters is highly variable and ranges from 5 - 250feet (2 - 75 m) depending on the prey species. Large food items are cracked by the flattened molars or pounded open with a rock and eaten individually while the sea otter fl oats on it’s back. Small prey items are often consumed whole. Foraging dives average 1-1½ minutes but sea otters are known to remain under water for up to 4 minutes at a time.

Sea otters’ average lifespan is approximately15 - 20 years. Female sea otters do not begin to breed until age 2 - 5 years and may breed annually up until age 20. Males become sexually mature at ages 4- 6 years but may not hold breeding territories until several years later. Mating occurs at all times of the year, and young may be born in any season .In Alaska, most pups are born in late spring.

Sea otters generally have a single pup during each breeding cycle and the gestation period can be highly variable due to delayed implantation of the fertilized egg. A pup will weigh from3 to 5 pounds (1.4 - 2.3 kg) at birth and stay with its mother from 3 - 6 months.

Historically, sea otters occurred in nearshore waters around the North Pacific rim from Hokkaido, Japan through the marine coastal areas of the Russian Far East and the Pacific coastal areas in the United States as far south as Baja California. The world-wide sea otter population was drastically reduced to just a few hundred animals between1742 - 1911, due to commercial harvest by the Russian and Russian/American fur trades. Three population stocks of sea otters exist in Alaska today. The statewide population is believed to number around 70,000animals

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sea otters are common off the coast of Alaska

sea otters have strong teeth to crush their food


Sea Otter	Walrus	Whale

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