The Sea Otter Foundation History Page 1

In the Beginning There Were Over 1,000,000 Sea Otters.

  Sea Otter History

by Michael B. Wells

 

“The most important keystone species known in the world may be the sea otter.”

                                                                World-renowned biologist Dr. Edward O. Wilson

The Sea otter is one of the most endangered and endearing animals on earth. They once thrived in near-shore coastal Pacific Ocean waters from central Baja, Mexico to California, Oregon, Washington, Canada, Alaska, Russia, extending all the way to the Sea of Japan. The sea otter is a keystone species, meaning when it disappears, other species become threatened. Caretaker of kelp forests, the otter’s stewardship is unique along its diverse coastal habitat. Having the distinction of a sentinel, or indicator species, otters act as a bellwether whose health gauges that of the entire near-shore ocean ecosystem. In their absence the oceans health has deteriorated and is threatened.

Southern and northern sea otters once numbered around one million before international trappers began hunting them for their soft, dense and valuable fur in the 1730’s, continuing until their virtual disappearance around 1906. Since that time their population has slowly rebounded, but after more than 100 years, only about 2,800 southern sea otters live in their current range along California’s central coast.

During that time, northern sea otters have fared better, especially in Alaska where there are now about 70,000, and Russia, where there are about 15,000. Still far below historical numbers, reestablishing both northern and southern sea otters into their native habitats could help ensure a healthier planet for current and future generations.

In the wild, sea otters live in colonies, sleeping in the water, often holding paws in groups and wrapped in kelp. These floating groups, known as ‘rafts’, keep them from drifting away from each other. Otters have a unique lung capacity two and one-half times the size of typical mammals on land. They are not sound sleepers, being easily disturbed in their turbulent natural environment. Males average over five feet head to webbed toe, typically weighing around 80 pounds, with some over 100 pounds. Females average about four feet in length, weighing around forty-five pounds.

Living up to twenty-five years, these carnivores feed primarily on a variety of bottom dwelling benthic invertebrates, such as crabs, clams, mussels, abalone, sea urchin, sea stars, fish and squid. Occasionally coming ashore to rest, they spend most of their time in the water.

Sea otters mate throughout the year. During mating, the male often bites the female on the nose, leaving scaring on many bred females. Births peak in the spring and fall, with gestation being about six months. After birth, the pup receives round-the-clock care from its mother. Young otters will spend much of their time on their mother’s belly as she floats on her back attending her pup. When the mother leaves to search for food, the pup will often cry out for her until she returns. When they are about six weeks old the pups are taught how to dive, and are weaned at 6 - 8 months. Mature females, around four years old, can pup annually, sometimes bearing twins.

Female otters live toward the center of the colonies, while males spend most of the time during winter and early spring separated from the females further north or south along the coast. A few dominant males maintain breeding territories within the clusters of females, but abandon them in the spring to join the other males at the outskirts, traveling as far as 60 miles up or down the coast. Otters can dive to a depth of over three-hundred feet searching for food and eat twenty-five percent of their body weight per day as required by their active metabolism to keep their bodies warm. To satisfy their high-energy lifestyle, otters are often searching for food.

Sea otters have baggy pockets of skin under their forelegs used to store food while swimming. Once floating comfortably on the surface, the otters will retrieve the catch and eat it on its belly. The unique, warm blooded mammals live mostly in the water without protection from cold by fat or blubber. Their source of warmth is their dense coat. With as many as 650,000 hairs per square inch, they possess the world’s densest fur. Otters constantly and scrupulously clean their coat, and spin on the water surface, capturing tiny air bubbles in their fur, forming an insulating blanket to keep warm in frigid ocean temperatures. Unfortunately, the thick fur can also be detrimental when oil spills occur, preventing the hairs from trapping air bubbles, thus preventing the warm-blooded mammals the insulation to protect themselves against cold ocean waters.

Additional primary threats to otter are fish net entrapment and the perceived conflict over resources. Fishermen don’t intend to catch the otters but they end up killing them in their nets accidentally and sea urchin divers claim the otters will reduce their source of income by eating too many urchin. This concern may be unfounded as the urchin flourished alongside otters for hundreds, if not thousands of years.

Meanwhile, scientists from the University of California, Santa Cruz and the state Department of Fish and Game discovered the deaths of more than twenty-one otters were caused by algae produced poison in fresh water sources that drained into the ocean. The poison is a liver-attacking toxin from Watsonville’s Pinto Lake and other tributaries. Otters are said to ingest the poison by eating shellfish near the estuaries affected by the algae.

Before they were nearly wiped out, about 16,000 otters are believed to have been living along California shores amongst the kelp forests. These underwater forests prevent erosion by absorbing wave impacts, while providing shelter and food for marine life. Without the otter protecting them, kelp forests are also in decline, along with the fish, lobsters, clams, abalone and sea urchins that call them home.

In The Diversity of Life, Harvard biologist Dr. Edward O. Wilson, internationally regarded as the ‘Dean’ of biodiversity studies, wrote “In places where sea otters disappeared completely, an unexpected sequence of events unfolded. Sea urchins, normally among the major prey of the otters, exploded in numbers and proceeded to consume large portions of the kelp and other inshore seaweeds. In otter times, the heavy kelp growth, anchored on the sea bottom and reaching to the surface, was a veritable forest. Now it was mostly gone, literally eaten away. Large stretches of the shallow ocean floor were reduced to a desert-like terrain, called sea-urchin barrens.” Unfortunately, the southern sea otter (Enhydra lutris nereis) population is now around 1% of historical numbers, they are found now living primarily in the approximately 150 mile coastline from Santa Cruz down to Pismo Beach, California.

Today otters are found in captivity at numerous zoos, aquariums and theme parks. The agile crowd pleasers exude a playful nature, swimming, diving and spinning through the saltwater. The highly charismatic animals use rocks as tools to open mussel and clam shells, otters are the only mammals other than primates known to use tools. 

 

 

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