Why Should We Care What Happens to a Small Mammal in the North Pacific?

By Neyssa Hays

As scientists learn more and more about certain species, it is becoming clearer that some are important for ecological structure and some species are good indicators of the health or illness of the area in which they live.  Sea otters are both and taking steps to protect them may be taking steps to protect us all.

Sea Otter with Urchin

Sea Otter with Urchin (France 2007)

Sea Otters as Keystone Species

The largest member of the family Mustelidae (minks, weasels, badgers, etc.), the charismatic sea otter (Enhydra lutris) is a well-documented keystone species because of their preferred food source: the spiny, purple sea urchin (Estes et al. 1982) A keystone species is a species that has a disproportionately large effect on its environment in comparison to its abundance.  Left unchecked, herbivorous urchins decimate kelp forests, leaving vast areas of ocean desert where once stood lush forests teeming with life (Estes et al. 1982 and 2010).  “Without any [other] natural predators,” wrote sea otter biologist James Estes, “urchins can become so numerous that they overgraze the lush kelp forests that otherwise abound along the West Coast. When this happens, the lost ecological benefits — both to society and the environment — are dramatic” (Estes 2012). Used by a plethora of ocean dwellers (including economically important species) for food, shelter, and rearing ground, the kelp forests are also critically central in maintaining coastline integrity and mitigating erosion (Estes et al. 2010).

Sea otter in the sun (France 2007)

Sea otter in the sun (France 2007)


Sea otters as Sentinel Species        

In addition to being a keystone species, sea otters have proven themselves to be a sentinel species, organisms whose welfare is indicative of the state of the environment in which they live.  As such, sea otter illnesses alert human welfare officials to potentially dangerous conditions along the coastline (Jessup et al. 2004).  If the waters in which they live are healthy, sea otters are as well, but with rising pollutants in coastal waters, protecting otter health has become increasingly difficult.  Fertilizer and pesticide runoff from lawns and farms; petroleum slicks from driveways, parking lots, gas stations, and tanker accidents; and diseases from domesticated animals are all taking their toll on the health of our oceans, and sea otter populations are showing the effects.  While birth rates have remained normal, mortality of adults is high and much of that has been from disease caused by contact with anthropogenic (of human origin) waste (Miller 2012), especially along coastlines with high human populations. This is particularly problematic for females who remain close to the waters in which they were born and are therefore exposed to the same contaminants through their entire lives (Jessup et al. 2004).

“All the research we have done to date suggests that there’s no one single mortality factor but that the deaths are caused by a suite of interacting stressors,” states Tim Tinker of the U.S. Geological Survey’s otter research program (Kettmann 2010).

Water pollution is hazardous to sea otters because of their life history patterns and habits, and each pollutant poses a distinct problem.  Because sea otters dive to hunt for and eat predominantly bottom-feeders (such as clams, crabs, sea urchin, and abalone) but spend most of their time floating on the surface, they come in direct contact with anything that is washed out to sea, including toxins and parasites from anthropogenic sources (Miller 2012). On the surface of the water where they spend most of their time, sea otters are exposed to oil slicks and toxic algal blooms, problems that have increased dramatically in recent years, while diving for their food requires swimming through other suspended pollutants.

Sea otters are born in and spend nearly their entire lives in the water, and though they are considered semi-aquatic by biologists because they are lacking features of fully aquatic mammals such as cetaceans (whales and dolphins) (Yeates 2007), their hind limbs are so well adapted for swimming, they are nearly useless on land (Kenyon 1969). Unlike other sea mammals, sea otters do not have insulative blubber but instead maintain thick pelage (fur) and a very high metabolism to ward off hypothermia (Yeates 2007).  If covered in petroleum, the otters’ thick fur loses its insulating properties and the animal soon freezes to death (Love 1992, Jessup et al. 2004, and Miller 2012).  Their high metabolism requires that sea otters consume prey at a rate of 25-35% of their own body weight each day; when the food the sea otters eat is contaminated, the contaminants become concentrated within the sea otters’ bodies, often to deadly levels (Jessup et al. 2004).  Because sea otters eat many of the same shellfish that humans do, their illnesses are potential indicators of problems in one of our own food sources.

In recent years, deceased and ill otters have shown high levels of the parasites Toxoplasma gondii, found in the feces of cats (Felis catus), and Sarcocystis neurona,  from opossum (Didelphis virginiana) feces (The Otter Project 2011, Righthand 2011, and Miller 2012).  Both cats and opossums were introduced to the Pacific coastal area by humans who brought them here as pets in the late 1800’s and early 1900’s, and have since become invasive (Maser 1998).  Scientists suspect that the fecal parasites, both related to malaria (Miller 2012), are washed out to the oceans through storm drains and, in the case of cats, through the sewage system when people dispose of cat litter in the toilet.

Sea Otters and Human History

Sustainably hunted for millennia by indigenous people of the Pacific Crest, when in 1741 Russia’s Vitus Bering and his crew first saw sea otters, the marine mammal’s populations were such that German naturalist Georg Wilhelm Steller stated, “They covered the shore in great droves” (Love 1992).  Like many other animals on the Endangered Species List, sea otters were then driven to near extinction in California as early as 1841 and elsewhere in their range by 1911 because of their economic importance to humans (Love 1992). Early explorers from Russia, Spain, England, France and the newly formed U.S. found great wealth to be made from the sales of the thickly furred hides that act as sea otters’ only insulation against the frigid waters of their natural habitat. Though sea otters are now legally protected from hunting and human encroachment in many areas, the protection of sea otters is still a contentious issue (Barlow 2012 and Estes 2012).

Map of the Pacific Crest Showing Sea Otter Historical and Current Ranges (USGS)

Map of the Pacific Crest Showing Sea Otter Historical and Current Ranges (USGS)

After they were listed as “threatened” in 1977, Southern sea otters (those living in the waters off the coast of California) were afforded protections.  U.S. Fish and Wildlife established sea otter reserves on San Nicolas Island, which they share with the U.S. Navy, and “no otter zones,” shellfish harvest areas from which “stray” otters can be captured and returned to their reserves (Kettmann 2010).  This theoretically keeps them from competing with human shellfish harvesters.  Recently the San Nicolas Island reserve area was challenged when Rep. Elton Gallegly introduced a bill to protect the Navy’s shooting rights on the island (Barlow 2012).  Neither environmental groups nor fishermen have ever been pleased with the “no otter zones;” environmental groups say the protections don’t go far enough while the fishermen rightly point out that the sea otters ignore the zoning laws (Kettmann 2010).  Similarly, in Puget Sound and the waters off Alaska, British Columbia, and Washington, where sea otter populations are generally healthy, state, province, and tribal fisheries managers struggle with balancing the welfare of the semi-aquatic mammals against that of the human fishing communities (Laidre and Jameson 2006).

Why We Should Care

Planetary ecology is like a lace cloth, delicate, intricate, and complex. Neither scientists nor politicians, nor the public, nor corporate leaders can completely predict what will happen if one or another species is protected or not.  But often times, as is the case with sea otters, protecting them starts a chain reaction of protection for other creatures, including ourselves.  As a sentinel species, sea otters’ well being is indicative of the health of the water in which they live, the same waters in which we play and fish. If not out of compassion for the wellbeing of other creatures, that healthier otters = healthier water = healthier humans should be enough of a reason to care about this small mammal of the North Pacific.

What We Can All Do to Help

Here’s the great news: there are many very easy things each of us can do to help improve the health of the oceans’ creatures, which in turn will help the health of every living thing on the planet, including our own.

1) Limit the amount of petroleum-based products you use by

a)         Walking or riding your bike to run errands; when commuting, take mass transit or ride your bike

b)         Use plant-based detergents, soaps, lotions and personal grooming products

c)         Reduce plastic in your life by using reusable grocery bags and glass food storage containers (such as peanut butter or jam jars)

d)        Purchase local, sustainably produced food

2) Keep chemicals out of storm drains by practicing organic gardening techniques and making sure your car or other gas-powered machines don’t leak oil or other fluids.

3) Bag your cat’s waste and used cat litter and send it out with your garbage; do not flush cat feces down the toilet.

4) Cut up the rings from beverage six-packs before throwing them away.

For more ideas on what you can do to help, visit The Otter Project at http://otterproject.wordpress.com.


Barlow, Z.  (2012, February 16).  Proposed bill addresses sea otter controversy.  Ventura county star.  Retrieved from http://m.vcstar.com

Estes, J. A., M. T. Tinker, J. L. Bodkin. 2010. Using Ecological Function to Develop Recovery Criteria for Depleted Species: Sea Otters and Kelp Forests in the Aleutian Archipelago.  Conservation Biology 24:852-861.

Estes, J. A., R. J. Jameson, E. B. Rhode. 1982. Activity and Prey Election in the Sea Otter: Influence of Population Status on Community Structure.  The American Naturalist 120: 242-258.

Estes, J.A. (2012, February 21). On Sea Otters, we need to see the big picture.  LA Times. Retrieved from http://www.latimes.com.

Jessup, D., M. Miller, J. Ames, M. Harris, C.. Kreuder, P. Conrad, J. Mazetz. 2004. Southern sea otter as a sentinel of marine ecosystem health.  EcoHealth 1:239-2004.

Kenyon, K. W. 1969.  The sea otter in the eastern Pacific Ocean.  Bureau of Sport Fisheries and Wildlife. Washington, D.C.

Kettmann, M. (2010, September 25).  The mystery of the vanishing California sea otters. Time. Retrieved from http://www.time.com.

Laidre, K. L. and Jameson, R. J. 2006. Foraging patterns and prey selection in an increasing and expanding sea otter population.  Journal of Mammalogy 87:799-807.

Love, J. A.  1992.  Sea otters. Golden, Colorado: Fulcrum Publishers.

Maser, C. 1998.  Mammals of the Pacific Northwest: from the coast to the high Cascades.  Corvallis, Oregon: Oregon State University Press.

Miller, M. 2012. Sick Sea Otters and Potential Health Risks for Humans at the Land-Sea Interface.  Abstract from presentation at the AAAS Annual Meeting, Feb. 18, 2012 in Vancouver, B.C.

Righthand, J. (2011, September). Otters: The Picky Eaters of the Pacific. Smithsonian magazine. Retrieved from: http://www.smithsonianmag.com.

The Otter Project 2010. “Sea otters where are you?” Sea Otter Scoop: The Official Blog of the Otter Project.  Accessed 2/18/2012 at: http://otterproject.wordpress.com

Yeates, L. C., T. M. Williams, T. L. Fink. 2007. Diving and foraging energetics of the smallest marine mammal, the sea otter (Enhydra lutris). Journal of Experimental Biology 210:1960-1970.

Image References

Armstrong, M. (2004, December 30). High tide strands sick sea otter.  Homer News.  Retrieved from: http://homernews.com

France, L. 2007.  Sea otters. Retrieved from: http://courses.washington.edu/mareco07/students/lindsay/Sea%20Otters.html

USGS, undated.  Sea otter range map.  Retrieved 3/8/2012 from: http://www.werc.usgs.gov/ProjectSubWebPage.aspx?SubWebPageID=1&ProjectID=91

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