Sea Otters
A sea otter floats along in Prince William Sound on a Discovery Voyages small ship cruise. Photo by Partick J. Endres
Compiled by Captain Rand, Discovery Voyages, Prince William Sound, Alaska
Here in Prince William Sound, Alaska, sea otters (Enhydra lutris) are one of our most frequently sighted marine mammals. They generally do not fear human presence, but are wary of fast moving boats, which could run into them. They are rarely seen on land, but are often swimming or sitting on small, floating pieces of ice. Although Native Alaskans are allowed to hunt sea otters for traditional and customary uses, here in the Sound they do not exercise these cultural rights often.
Geographic Range and Population
Sea otters’ geographic range historically extended in an arc from northern Japan, northward along Russia’s Kuril Islands and Kamchatka, then east to Alaska’s Aleutian Islands, Kodiak Island, the coast of mainland Alaska, southeast into the panhandle of Alaska, and further southward along British Columbia’s coast and all the way down to Baja California Peninsula in Mexico.
The vast coast of Alaska, at 35,000 miles in length, is home to ¾ of the world’s population of sea otters. Here, along the storm-protected and nutrient-rich 3,000 miles of shoreline in Prince William Sound, live over 10,000 sea otters. Seen in rafts of a few to 50 or more, sea otters have been spotted by the Discovery in large resting groups: the largest raft we’ve seen so far included over 200 animals. They are common in Prince William Sound and seen regularly on our tours, often hauled out on small flat pieces of glacial ice which has recently fallen from the face of our many tidewater glaciers.
Original population estimates placed their population between 150,000 and 300,000 animals. In the mid 1700’s, Russian-funded explorers, Vitas Bering and Georg Steller, discovered sea otters as a fur resource and soon after began the “great hunt”. In the coming years, Russian, British, and American fur trading caused the sea otter population to collapse, leaving only 1,000 – 2,000 animals worldwide.
Two sea otters perch atop ice floes in Prince William Sound on a Discovery Voyages small ship cruise. Photo by Patrick J. Endres
Fur Trade
On a side note … this international fur trade was one of the world’s earliest forms of globalization. Manufactured goods, like axes, shovels, nails, and other tools, as well as textiles like wool blankets and clothes from England or the east coast of North America, were transported via sailing ships from the Atlantic, around the southern tip of South America, to the Pacific Northwest Coast, where they were traded with native peoples for sea otter pelts, and occasionally beaver pelts. Once emptied of their manufactured trade goods and filled with furs, the ships sailed on to Hawaii for fresh water, food, and in some instances, visits from Wahines (the Hawaiian and Maori word for woman). From here, the ships loaded with furs continued westward across the Pacific to China, where sea otter pelts were prized by Chinese aristocrats for their superior warmth. There, the furs were traded for Chinese manufactured goods, which were in demand back in England and colonial America. It seems that the Chinese had developed a highly successful process of firing their porcelain at higher temperatures, resulting in exquisite and globally popular pottery available nowhere else. After trading their shiploads of furs for china, the English and American traders headed home, where profits of up to 2000% awaited them.
This global trade was referred to as “The Golden Route,” and took 2 years of travel and trade to complete. It, of course, ended with the demise of the sea otter population in the early to mid-1800’s. Through an international ban on hunting, conservation efforts, and programs designed to reintroduce sea otters to previously populated areas, their numbers have rebounded to over 100,000 animals.
Sea otters swim together in Prince William Sound, Alaska. Photo by Patrick J. Endres
Physical Characteristics and Diet
Sea otters are much larger than their cute and cuddly pictures make them appear. On average, males are 5 feet long and weigh up to 100lbs, while females are 4 feet long and weigh about 70lbs. They can grow to be 20 years old. On the Alaskan coast, they feed on various bottom-dwelling animals like crabs, sea urchins, clams, mussels, sea stars, tube worms, and the occasional finfish, like salmon or cod. Otters have a high metabolic rate (2 – 3 times that of a comparatively-sized land mammal) and need to consume approximately 20% or more of their body weight in food per day. (For a human, this would be like eating 20 – 40 pounds of food each day!)
My friends in the scientific community will argue that they have never seen sea otters eating crabs. Friends in the commercial crab fishing industry say that the sea otters ate them out of a job. I think they’re both somewhat correct. Scientists haven’t seen otters eating crab because the otters ate them all before the scientific community got out into the Sound to watch! The commercial fishing community may have compounded the problem of crab resource collapse by continuing with the same catch rate year after year without figuring in the increasing take of crab by the burgeoning population of hungry sea otters eating year round.
Sea otters’ lung capacity is 2.5 times greater than that of a similar sized land mammal. They are capable of diving 300 ft. down in search of food. They propel their long bodies along in the water by undulating their entire body and kicking with their large rear flippers. Their front paws are quite small and almost hand-like in that they use them to forage for and hold food. They also use those handy little front paws for hanging onto other sea otters, like mother sea otters do with their pups, and like males do when trying to mate (although males also bite and hold onto the nose of their female mate in order to make certain that she doesn’t get away).
A sea otter regards us with characteristic curiosity from an iceberg in Prince William Sound, Alaska. Photo by Hugh Rose
Classsification
Sea otters are divided into 3 subspecies: the Asian sea otter, the Southern sea otter, and the Northern sea otter (which is the one we have here in Alaska and the one I mostly write about in this overview).
Sea otters are not grouped with seals and sea lions as you might expect, but are in fact the largest member of the weasel family. Locals jokingly refer to them as sea weasels. Interestingly, they are also the smallest of marine mammals. Unlike most other marine mammals, instead of relying on blubber to keep them warm, sea otters rely on their fur. Theirs is the thickest fur of any mammal, at one million hairs per inch! The fur catches and holds air bubbles blown into it during grooming, which act as another layer of warmth. Because of their fur’s importance to their survival, sea otters can often be seen grooming themselves. Their skin is not attached to their skeletal or muscle tissue, allowing them to pull their fur from all the way around their backs for cleaning and maintenance.
Three sea otters lounge on an ice floe. Photo by Gerald Corsi
In the Wild
Like sea lions, sea otters can be a hassle to commercial fisheries – they are known to compete with shellfisheries and to get tangled in coastal gill nets. However, they are reputed to be rather “Houdini-like” in their abilities to extract themselves from nets when they do become entangled. Here in the Sound, we have several oyster farms the largest of which is owned by our good friend Oyster Dave. In 20 years of operation, Dave has never experienced any problems with sea otters getting into his oyster baskets, which are the net enclosed growing platforms for his shellfish.
However, when sea otters pioneered their way back into Prince William Sound a number of years ago, there were several viable commercial crab fisheries including king crab, tanner crab, and Dungeness crab, which all contributed to local community economies. As the sea otter population grew, the crab stocks fell. It seems that crabs must molt (shed their shell so as to grow a larger one) in order to mature, and that this molting takes place in near shore shallow waters, where they are easy prey to the ever- hungry sea otter. Additionally, young crab spend the first few years of their life cycle in those same near shore shallows, where they are again vulnerable to the swift and talented near shore sea weasel.
Two sea otters wait expectantly on an ice floe in Prince William Sound, as seen from a Discovery Voyages small ship cruise. Photo by Patrick Endres
Sea Otters at Risk in the Wild
The 1989 Exxon Valdez oil spill was directly responsible for the loss of thousands of marine mammals, including sea otters in the Sound. Decades later, there still seem to be problems with localized otter populations in areas which were heavily oiled in 1989. There appears to be an unanticipated slow recovery of sea otter numbers in these previously oiled shores of the Sound, but the scientific community continues to monitor conditions and population numbers.
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