The Yamhill Rivers Nature Reserve: a Proposal

By Neyssa Hays

Introduction

     The South Yamhill and Yamhill Rivers combined run through 71 miles of Northwest Oregon farmland and small towns, including Sheridan, McMinnville, Dundee, and Dayton (from west to east). A tributary of the Willamette River, the bi-river system has become an important spawning ground for the threatened and evolutionarily significant unit (ESU) of Oregon Coastal Coho Salmon (Oncorhynchus kisutch) as well as a winter refuge for Chinook Salmon (O. tshawytscha) smolts and juveniles, and the historic grassland prairies surrounding the lower sections were home to the endangered Fender’s Blue Butterfly (Icaricia icarioides fenderi) as well as other enlisted species (Good et al. 2005, McIntire et al. 2007, Togstad 2011).

     Creating the Yamhill Rivers Reserve, a nature reserve that stretches the length of the South Yamhill and Yamhill River system at a width of at least 300 feet on each side of the river, would form a riparian zone of 5370 acres of contiguously protected habitat with minimal loss of agricultural land for any one farmer or business. In addition, adding a parcel of roughly 700 acres along the river that includes a small wetland area would provide land that could be restored to oak savannah and grassland prairie habitat.

     The source of the South Yamhill River is located at coordinates 45.110556, -123.727778, in the foothills on the east side of the Coast Range, at an elevation of roughly 551 feet (Google maps 2012). The river then flows east. By the time it joins with the North Yamhill River to become the Yamhill River, it has dropped to an elevation of 75 feet; the Yamhill River continues the descent to 59 feet at its confluence with the Willamette River. The Yamhill Basin watershed varies in elevation from a high of over 3400 feet at the peak of Trask Mountain to a low of roughly 59 feet at the confluence of the Yamhill River and the Willamette River (Bash & Ishii, eds. 2002). The watershed, including the Yamhill River system, was carved into rolling hills and an expansive flatland by the Missoula Floods, which also deposited granite, quartzite, and slate. The river floodplains are composed predominantly of deep alluvial deposits of sand, gravel and silt over sedimentary rock. Average annual rainfall is 50 inches or less, most of which falls between November and March; temperatures are mild with mean winter temperatures in the low 40’s (F) and high summer temperatures averaging in the low 80’s (F).

Conservation Aims

     Over the last twenty years, the population of Yamhill County has experienced a higher growth rate compared to the rest of the state and is predicted to grow from 101,000 to nearly 156,000 people over the next thirty years, with the highest concentrations in the towns near the South Yamhill River (Bash & Ishii, eds. 2002). As populations grow, pressure to subdivide and build on the land along the river will increase. Most of the land surrounding the Yamhill River system is currently farmed, and while some farmers allow a wide margin between plowed land and the river, many farmers work the land within a few feet of the embankment, a practice that leads to high soil erosion, muddied rivers, warm water temperatures, and higher run-off of farm chemicals (fertilizer, pesticides, and herbicides). Creating a wide, protected riparian zone would buffer the rivers from these effects and will ensure a healthier ecosystem for future generations.

     In addition to safeguarding habitat for Coho Salmon and Fender’s Blue Butterflies, the Yamhill Rivers Reserve would protect several other species, including plants, insects, birds,amphibians, mammals, and other fish (some threatened or endangered, others of concern; USFWS 2012). Threatened and endangered plant species that would potentially benefit from this reserve are Water Howelia (Howelia aquatilis), Willamette Daisy (Erigeron decumbens var. decumbens), Kincaid’s Lupine (Lupinus sulphureus ssp. kincaidii), and Nelson’s checkermallow (Sidalcea nelsoniana; CPC 2010). The last two plants are important food sources for the Fender’s Blue Butterfly. Other species of concern that may benefit from the reserve include the Streaked Horned Lark (Eremophila alpestris strigata), the Southern Torrent Salamander (Rhyacotriton variegates), the Long-eared Myotis Bat (Myotis evotis), Coastal Cutthroat Trout (Oncorhynchus clarki ssp) to name a few.

     The most obvious landscape features of interest for the Yamhill Rivers Reserve are the rivers themselves. Historically, the rivers wound through habitats such as mixed conifer-deciduous foothills and oak savanna (Bash and Ishii, eds. 2002). The latter of the two is perhaps the least obvious landscape feature of interest considered in this plan, though of high significance. Oak savanna and associated grassland prairie were once abundant habitats throughout much of North America and provide important food sources and refuge for a variety of organisms, including Fender’s Blue Butterfly, Streaked Horned Lark, Pygmy Rabbits, game birds, deer, and many others. Because the land on which they grow is prized for agriculture, today less than 0.5% of natural prairies and oak savanna remain and much of that has been severely affected by invasive species (McIntire et al. 2007).

Rationale

     In 1996, the Oregon State University Extension Service surveyed Yamhill County residents and found that over 90% of respondents supported continuing strategic planning for water quality and watershed management (Bash and Ishii, eds. 2002). The South Yamhill River is listed under section 303 of the Federal Clean Water Act with concern over water quality issues including “[high] temperature, flow modification, and bacteria,” all having harmful effects to many stream organisms, including salmon. Riparian zones counter all of these negative effects, and the longer and wider the continuous zone is the more effective it becomes. Cool water temperatures are of utmost importance throughout the salmon life history and deep riparian zones with tall trees are ideal for shading and cooling rivers and streams. Recent studies in Ireland have shown that a mix of dense canopy and sporadically open areas create conditions beneficial to macroinvertebrates that are important food sources for salmon (McCormick and Harrison 2011); this condition can be created in the initial stages of the reserve through the planting of fast-growing, large native riparian species such as alder, willow, and cottonwood as well as smaller shrubs such as elderberry and spirea. As riparian zones age, debris from falling trees and other plants serve to modify the water flow and offer refuge to fish and other animals. The root systems of the plants and soil of riparian zones act as natural filter systems against bacteria and chemical pollutants.

     In addition to maximizing the filtering system described above, the 300-foot width of the Yamhill Rivers Reserve is necessary to encourage species diversity. It is currently standard practice (and law in many countries and states in the US) in the timber industry to leave a riparian buffer when cutting timber; such buffer strips vary in width from an average of 50 feet to a high of 165 feet (Whitaker and Montevecchi 1999 and Lee et al. 2003). While studies have shown that these widths are ample to moderate edge effects on trees along riverbanks, response of bird  populations varies with width of riparian zones (Whitaker and Montevecchi 1999 and Harper et al. 2007). Whitaker and Montevecchi (1999) found that in riparian buffer zones of any width populations of birds generally associated with river habitats resembled those of uncut river areas. Interior forest bird populations, however, increased somewhat with increasing width, and the scientists postulated that it was likely that wider riparian buffer zones would have a positive influence on these populations.

     Similarly, studies of Fender’s Blue Butterflies have shown that populations respond positively to larger patches of habitat (McIntire et al. 2007). Studies over a ten-year period followed by model simulations indicate that increasing butterfly refuges to at least 340 acres of connected patches have the potential to increase populations from the current 5,000 individuals to upwards of 65,000. Prairie acreage of this size would also be beneficial to the Streaked Horned Lark, which has been shown to require open areas of over 300 acres to support a healthy nesting population (FWS 2011). The remaining ~350 acres of the 700 acres planned would be restored to oak savanna, which would serve a variety of native animals that have lost most of their habitat to farming during the last two centuries.

Trophic Level Considerations

     Players in the trophic levels will depend to some respect on whether they are aquatic or terrestrial species, although there are certainly crosses as well. In the river, the top trophic level is most likely to be the salmon; with smaller fish and macroinvertebrates at the second level; and in the first level a combination of detritus (including salmon carcasses), higher level plants, and algae.

     The Yamhill River system was previously “cleaned” of woody debris used by all trophic levels as habitat, food, or substrate; subsequent winter flooding washed away gravel imperative to spawning (Bash and Ishii, eds. 2002). Management actions will include planting of fast growing, tall species of trees as well as slower growing trees to provide shade and eventual deadwood for all trophic levels. It may be necessary to include woody debris in the initial restoration projects as well as laying down appropriate gravel.

     Terrestrial primary producers along the riparian corridor will include black cottonwood, alder, willow, and understory plants such as elderberry and spirea in the initial stages, followed by such slow-growing species as big-leaf maple, bitter cherry, Douglas fir, and western red cedar. Some early producers and saplings of slow-growing species will require being planted while others will likely self-propagate once the land is no longer being cleared for farming. The oak savanna and grassland prairie will need to be extensively planted with native species and monitored for control of invasive species. Herbivores, the second trophic level, will include Pygmy Rabbits, Pocket Gophers, several species of birds, deer, and Fender’s Blue Butterflies; some of these species, such as deer, will arrive autonomously while the populations of others, such as Pygmy Rabbits and Fender’s Blues, will need to be transplanted after the plants are well established. Likely the top trophic level will be dominated by coyotes and foxes, but will also include birds such as osprey, hawks, eagles, and owls as well as minute predators such as Myotis Bats. It is not out of the question, however, that cougars would also use the riparian corridor, though this is likely to take several years.

Stakeholder concern

     Of greatest concern to stakeholders would be the loss of land used for farming, timber, or development. A square acre is 208 feet per side, and one mile is 5280 feet long; so for every mile of riparian zoning, a landowner would stand to lose roughly 38 acres on each side of the river. Additionally, much of the upper end of the river runs through land owned by the Confederated Tribes of Grand Ronde or its members. While they may be supportive of this  plan, many of their tribal members are farmers and would be hard-pressed to give up their farmland for a nature reserve. In the bottomland of the river about five miles west of McMinnville, Riverbend Landfill operates right up to the edge of the river and in the last few years management expanded their operation, putting in a state-of-the-art waste disposal system.

     Further down river, the South Yamhill flows directly through McMinnville and in several places the highway and other roads cross over. These areas cannot be protected or restored at present and it is not likely that they will be in the future either. However, local planners are already establishing urban growth boundaries (UGB’s), which could include riparian zoning (Bash and Ishii, eds. 2002). Throughout the watershed, water quality would benefit by replacing culverts with bridges.

Management

     The first management actions would be to make the proposal to the community and listen to the concerns of the primary stakeholders. Management would need to educate the stakeholders on the benefits of riparian buffering and healthy water systems, such as reduced flooding and bank erosion, and decreased need for fertilizing because the riparian zone would support more native pollinators. Perhaps there could be incentives for stakeholders to support the plan as well. Likely, the 700-acre parcel for oak savanna and grassland prairie would need to be purchased. All involved parties then would try to come to an agreement.

     Once the area is established, subsequent management actions should be first to design and carry out initial water quality and wildlife studies. Once a baseline is established, management will engage in removal of invasive species, planting native species, and continued monitoring of the ecological health of the area. Additionally, stakeholders will be invited to regular informational meetings to discuss progress and concerns.

Future Predictions

     The 100-year predictions for Pacific salmon are dire, with most populations in the lower latitudes going extinct due to climate change. However, if river systems such as the Yamhill can be set-aside as salmon sanctuaries and the waters cooled enough, the salmon stand an increased chance of survival. Many of the tree species of older riparian corridors are long-lived species with varying growth rates. In 100 years a Douglas fir may have reached nearly its full 230 feet and stand another 800 years growing slowly in diameter, while the oaks in the savanna will have only reached half of their full 85 feet and may persist another 250 years. Several of the oaks in the savanna will have lost limbs and become hosts for cavity dwellers, including Wood Ducks, Acorn Woodpeckers, and bats. Along the river, Black Cottonwoods would likely out-compete the Red Alder and dominate the embankment. Logs and debris from fallen trees as well as water-loving willows will have created a complex river scene. McIntire et al. (2007) predicted populations of Fender’s Blues in a 300-acre system would stabilize after 25 years to between 50,000 and 65,000 individuals. Other populations of short-lived species such as songbirds, bats, and rodents will likely have reached their carrying capacity as well and will have settled into relatively stable populations. Longer-lived species such as deer and coyotes will likely still be increasing in population.

     In 1000 years the area will have experienced some climax communities and some of the Douglas firs would be nurse logs for species such as Western Hemlock as well as under-story plants such as huckleberry, salal, and snowberry. Pileated woodpeckers will likely be heard searching for food and making homes in snags and diseased trees. The oak savanna as well will have seen replacements and successional changes. Historically oak savanna and grassland prairies were maintained through fire, both controlled and natural. It is conceivable that future management practices would also include controlled fire; this would have the desirable effects of removing many invasive species and ridding the area of tree-damaging fungus and disease.

Potential Impacts

     Because Coho Salmon are not native to the Yamhill River system, it is possible that  their increased presence would have a negative effect on other species in the river system. The Coho currently spawning in the Yamhill Rivers are naturally returning descendents of released fish from a far-off hatchery, a practice that was discontinued in 1997 after nearly fifty years (Togstad 2011). However, on a whole, wild Pacific salmon numbers are dwindling for many reasons, including climate change, over-fishing, and competition with hatchery-reared salmon; supporting populations that are now naturally spawning has the potential for preserving a species that is struggling in its historic rivers. Other impacts of the riparian zone include higher biodiversity, decreased run-off, and cleaner, cooler waters.

     The Yamhill Rivers Reserve would improve water quality in the South Yamhill and Yamhill Rivers, and increase Coho salmon and Fender’s Blue butterfly populations for many future generations. Moreover, it could become a model for riparian management systems throughout the Pacific Northwest and beyond.

 

Resources

Bash, J. and J. Ishii, eds. 2002. Upper South Yamhill River watershed assessment. Oregon Watershed Enhancement Board 1-115. Accessed 4/25/2012 at: http://nrimp.dfw.state.or.us

CPC. 2010. Center for Plant Conservation Website. Accessed 4/20/2012 at: http://www.centerforplantconservation.org

FWS. 2011. Species Fact Sheet Streaked Horned Lark Eremophila alpestris strigata. Fish and Wildlife Services. Accessed 5/30/2012 at: http://www.fws.gov

Good, T.P., R.S. Waples, and P. Adams, eds. 2005. Updated status of federally listed ESUs of West Coast salmon and steelhead. U.S. Dept. Commer., NOAA Tech. Memo. NMFSNWFSC-66, 598 p.

Lee, P., C. Smyth, and S. Boutin. 2004. Quantitative review of riparian buffer width guidelines from Canada and the United States. Journal of Environmental Management 70:165-180.

McCormick, D. P. and S. S. C. Harrison, 2011. Direct and indirect effects of riparian canopy on juvenile Atlantic salmon, Salmo salar, and brown trout, Salmo trutta, in south-west Ireland. Fisheries Management and Ecology 18:444-455.

McIntire, E. J. B., C. B. Shultz, and E. E. Crone. 2007. Designing a network for butterfly habitat restoration: where individuals, populations and landscapes interact. Journal of Applied Ecology 44:725-736.

Togsad, J. 2011. Simple way to save salmon: Conservation District helps landowners improve conditions for fish in local streams. The News Register May 21, 2011. Accessed 5/30/2012 at: http://www.newsregister.com

USFWS. 2012. Federally listed, proposed, candidate species and species of concern under the jurisdiction of the Fish and Wildlife Service which may occur within Yamhill County, Oregon. Accessed 4/18/2012 at: http://www.fws.gov/oregonfwo/Species/Lists/Documents/County/YAMHILL%20COUNTY.pdf

Wondzell, S. M., M. A. Hemstrom, and P. A. Bisson. 2007. Simulating riparian vegetation and aquatic habitat dynamics in response to natural and anthropogenic disturbance regimes in the Upper Grande Ronde River, Oregon, USA. Landscape and Urban Planning 80:249-267.

Whitaker, D. M. and W. A. Montevecchi. 1999. Breeding bird assemblages inhabiting riparian buffer strips in Newfoundland, Canada. Journal of Wildlife Management 63:167-179.

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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.

References

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