Southern Sea Otter < enhydra lutris nereis > // Ashley Chen

image 1

Listed date: April 3, 2003

Type of Listing: Threatened

Where: California, wherever found

Summary                                                            

image 2

Southern sea otters have been listed as threatened since 1977 under the Endangered Species Act. Before the 18th century, Southern sea otters were primarily location along the North Pacific Rim from Hokkaido, Japan to Baja California, Mexico. Presently, they have reclaimed approximately 13% of their historic range. Their current population is about 2,150 animals ranging from Half Moon Bay to Point Conception along the coast of California. 

image 3: Southern sea otter self grooming

These playful mammals are actually one of the smallest marine mammals- adult females and males grow to be about 46 and 64 pounds respectively and live to be approximately 4-6 years of age. Southern sea otters have very little fat so they rely heavily on their clean, dense, water resistant fur. To stay warm within the cold waters, these sea otters maintain high levels of internal hat to make up for their lack of fat and use their fur as insulation. The result of oil contamination on their fur is damaging because it reduces the insulting quality and leads to hypothermia and death.  

Southern sea otters consume about 20-25% of their body mass per day in order to fuel their energetic personality and spend around 20-50% of their day foraging for food. They mostly eat marine invertebrates such as sea urchins, clams, mussels, abalone, mollusks, crustaceans, and snails. The otters travel in groups called “rafts” which are made up from two to 20 animals. They usually prefer areas in the ocean with surface kelp canopies but are occasionally found in open waters. The gestation period of Southern sea otters are about 6 months with the peak period of pupping occurring from October to January and a second peak from March to April. Females almost always give birth to a single pup and it is taken care of for around 6 months. Since females predominately take intensive care of the pup, a lot of their energy is used as they also have to forage for extra food. All this extra work decreases the female otters’ energy which leaves them more susceptible to additional stressors such as parasite infections or aggression by male otters. 

image 4: Southern sea otter eating sea urchin

Geographic and Population Changes  

image 5: geographic range of Southern sea otters

From the 18th to 19th century, fur trade was common and resulted in a decrease of Southern sea otters along the coast of California. After the otters got protection from the International Fur Seal Treaty of 1911, sea otters diversified in geography, expanding further to the North and South along the central coast of California. In 2003, high mortality rates of the sea otters resulted in a slow rate of population growth. Researchers found that sea otters in central California were at or near their carry capacity for the local environment, resulting in a lack of growth. After studies were done through modeling analysis, scientists found that the spatial configuration of the available habitat and high degree to spatial structure within sea otter communities lead to a population growth with rates that differed from expected patterns. In addition, there were unusually high numbers of stranded Southern sea otters found in 2003. No specific cause has found to be responsible for this rise in stranded otters but the intoxication by domoic acid from the blooms of alga pseudonitzschia australis was found to be a possible contributor. The blooms of this alga was also found to be related to cardiac disease within Southern sea otters. 

Geographically, Southern sea otters currently reside along the coast of California from approximately Half Moon Bay to Point Conception. They are often found within 2 km of the shore and forage in rocky and soft sediment areas.

    

Cause of Listing & Main Threats               

The listing of Southern sea otters is primarily due to habitat degradation, such as oil spills, and human activities, like entanglement in fishing nets, which impact the otters. Sea otters are very vulnerable to oil spills from coastal tankers, which is a primary human related reason why the otters are listed. The otters become hypothermic when their fur is slicked with oil from the spills as it ruins the insulation property of their fur. In addition, many otters ingest the oil stuck on their fur while they are self grooming, resulting in gastrointestinal disorders as well as possible lung damage. One example of this is the Exxon Valdez spill in Prince William Sound which resulted in the death of 1,000 to 5,500 Southern sea otters within the first few months of the spill. Oil spills increase the contaminants of DDT, DDE, and PCBs found in stranded Southern sea otters. 

image 6: Southern sea otter covered in
oil from the Exxon Valdez oil spill

Another human activity that is negatively impacting Southern sea otters is commercial fishing, A 2003 study found that the increase of sea otter mortality was linked to summer commercial fishing through incidental captures. Severe weather and occasional climatic events like El Niño are disruptive to sea otter foraging practices and may lead to a depletion of food availability, further decreasing pup survival rates. Infectious diseases within the sea otter community has lead to serious tooth wear in older sea otters, which is another factor in increased mortality rates. The climate change umbrella is also a factor that is negatively impacting Southern sea otters. Ocean acidification in the North Pacific, pathogen transport, marine invasive species, and the increase in intensity of storm events has been noted to have detrimental effects on Southern sea otter communities.

Recovery Plan                                                   

image 7: mother and pup Southern sea otters

Southern sea otters are protected by the Marine Mammal Protection Act of 1972, which is beneficial to directly preserve the otters aside from environmental and human activity impacts. The objective of the Southern sea otter recovery plan is to regulate and control human activity which often places sea otters in jeopardy due to habitat destruction and various other impacts. The ultimate goal of the recovery plan is to recover the Southern sea otter and de-list the species. The sea otter will be delisted once it reaches an average population that is greater than 3,090 animals over a 3 year span. 

Some actions to take include:

• closely monitor the demographics of the Southern sea otter to document their population size, rate of change, and distribution
• study habitat and note any changes in type, abundance, distribution, and use or general change in carrying capacity by collecting data and mapping habitat types
• perform research to gain understanding of factors that are preventing the population growth of the sea otters — see what actions can further be taken to ensure success in delisting of Southern sea otter
• research and implement plan to reduce risk of oil spill within sea otter ranges
• find ways to limit effect of spill on otter population if one does occur, 
• establish public education & outreach programs to limit recreational related issues upon sea otters and to raise awareness and understanding of the sea otter community

What Can You Do?                                          

You can help by taking action to join different environmental protection groups such as different Marine Conservation Organizations or the National Wildlife Federation. By following up with these groups you will be up to date with the recovery process of the Southern sea otter and continue to advocate for their de-listing. In addition, it is so useful to educate yourself on the status of these threatened otters. By educating yourself you will be able to pass your knowledge onto others by bringing it up in conversations and answering any questions your peers may have. Another way you can raise awareness is to create a blog like this one and share it on social media. This will allow for others to gain understanding and awareness of environmental issues that are present. You can also donate to the California Sea Otter Fund to improve ocean habitats and protect sea otters. 

Additional Resources                                    

National Wildlife Federation

US Fish & Wildlife Service on Southern sea otters

US Fish & Wildlife Services on Endangered Species

Animal Diversity Web 

Non-profits on Marine Conservation

Marine Conservation Organizations 

Sources                                                                                           

• http://www.iucnredlist.org/details/7750/0
• https://ecos.fws.gov/ecp0/profile/speciesProfile?spcode=A0A7
• https://www.fws.gov/ventura/docs/species/sso/Southern%20Sea%20Otter%205%20Year%20Review.pdf
• https://alaska.usgs.gov/science/biology/nearshore_marine/evos.php
• https://www.fws.gov/ventura/endangered/species/info/sso.html

images:

1: https://www.montereybayaquarium.org/-/m/images/animal-guide/marine-mammals/southern-sea-otter.jpg?bc=white&h=822&mh=916&mw=1222&w=1093&usecustomfunctions=1&cropx=0&cropy=45
2: http://bento.cdn.pbs.org/hostedbento-prod/gallery/20150818_202516_557832bbl_otter-gallery_1.jpg.1280x720_q85.jpg
3: https://www.mmc.gov/wp-content/uploads/15259513562_89a69fafd6_o.jpg
4: https://closetstudioblog.files.wordpress.com/2013/03/tanu-eat-urchin-john-healey-1-resize-2.jpg
5: https://ecos.fws.gov/docs/recovery_plan/030403.pdf
6: https://grist.files.wordpress.com/2014/03/sea-otter-flickr-mike-baird.jpg?w=1024&h=576&crop=1
7: https://www.montereybayaquarium.org/-/m/images/conservation-science/sea-otter-great-tide-pool.png?la=en