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Sea Otters

Sea otters are the smallest of all marine mammals. At birth, they are about 22 inches long and weigh approximately five pounds. Adult males grow to be about 58 inches long and weigh 60–85 pounds. Unlike other marine mammals, sea otters do not have a protective layer of blubber to shield them from cold water. To compensate, they have extremely thick fur that traps warm air between hairs and insulates the body.

Sea otters consume approximately 20% of their body weight in food daily. They dive to the bottom of their shallow shoreline habitat to feed upon sea urchins, clams, oysters, and other shellfish. Only strong males are able to catch fish. The otters return to the surface with their prey, float on their backs, and strike the shellfish together or against rocks to pry them open.

Sea otters have a strong influence on coastal ecosystems. They restrict the sea urchin populations in near-shore habitats, allowing kelp forests to flourish (sea urchins graze heavily on kelp). It's easy to see where sea otters thrive: Just look for abundant kelp. Pups are born (generally one per litter) after a six-month gestation period and remain with their mother for 12 weeks. Fathers play no role in the offspring's upbringing; the two sexes tend to remain separate except when breeding.

There are three subspecies of sea otters. The Southern, or California, sea otter (Enhydra lutris nereis) is represented by only one population in California and is declining at a disturbing rate. The Northern sea otter (Enhydra lutris kenyoni, found in Washington, Alaska, and Canada) and the Russian sea otter (Enhydra lutris lutris, found in Russia and Japan) are also facing conservation threats.

Seals

True seals (a group that doesn't include the fur seal) belong to the family Phocidae. Seals lack ear flaps and the ability to rotate their hind flippers forward to walk on land, which sea lions can do. Instead they pull themselves forward by their fore flippers, dragging their hind flippers behind them, with an inchworm-like motion. In the water, however, they are amazingly graceful, using their hind flippers in a sculling motion to propel themselves while steering with their front flippers. Some species are deep divers—the northern elephant seal dives regularly to approximately 2500 feet and stays under routinely for 20–30 minutes per dive.

Seals give birth to one pup each year, nursing for a brief, intense period (anywhere from one month to a mere four days), before abruptly weaning their fat offspring and returning to the sea to feed. In the majority of seal species, the mother does not feed while nursing, so she loses weight and needs to rebuild her blubber stores after weaning her pup. The pup is left to learn to swim and to hunt fish and squid on its own, while living off fat stores. Guided almost entirely by instinct, the pup makes the transition from utter dependency to independence.

Male seals generally compete to control access to females and usually mate in the few days before the females return to sea after weaning her pup. The embryo will begin to develop, but then remain suspended in the womb (this is called delayed implantation), until a female has rebuilt her blubber stores. Gestation is therefore about nine months, although female seals give birth at almost exact one-year intervals.

Seals are found in all waters of the world, from the Arctic and Antarctic to temperate and tropical waters.