Southern sea otter - Hope Young

The Southern Sea Otter (Enhydra lutis nereis)

[Fig. 1]

Description & Ecology of Organism - Sea otters are unanimously loved for their adorable, and seemingly cuddly, appearance. Their rounded faces, big eyes, and little black noses create the image of an animal that could do no harm to another organism. However, the sea otter species (Enhydra lutris) has readily adapted into an avid marine hunter. At an average length of four feet, they are the largest member of the Mustelidae (weasel) family, yet the smallest marine mammal in North America.

Sea otters do not have blubber or a significant amount of fat on their bodies so they must rely on extremely dense fur to keep them warm and dry. Otters typically reside in hard- and soft-sediment habitats, like protected bays and exposed outer coastline. They use their sleek bodies and webbed feet to dive down to depths up to 200 feet in order to capture their prey. Sea otters are also one of the only mammals known to use tools for hunting and eating their food. Sea urchins, crabs, clams, and more marine invertebrates don’t stand a chance against the rocks that sea otters have learned to use [Fig. 3].  

[Fig. 2]

Geographic & Population Changes - 

The entire sea otter species used to reside across the globe, ranging from the Eastern islands of Japan all the way down to Baja, California. A plethora of threats including overexploitation, disease, and habitat degradation, broke up the species into two main subspecies, northern and southern sea otters (Enhydra lutis nereis). The southern sea otter has a current population total of about 2,150 animals that ranges from Half Moon Bay to Point Conception, California. Based on scientific analyses of sea otter carrying capacity, the minimum number of individuals in a population (at optimum levels) should be around 8,400. The species had an estimated population of 16,000 individuals up until the fur trade, which nearly decimated sea otters entirely.

[Fig. 3]

Listing Date & Type of Listing - The Southern sea otter was listed as “threatened” in 1977 under the Endangered Species Act. They were placed under recovery priority 9C, meaning that they are a subspecies facing a steady level of threat but have a high potential for recovery. They were also recognized as “depleted” under the Marine Mammal Protection Act.

Cause of Listing & Main Threats to Continued Existence - Southern sea otters were listed as “threatened” because they have such a small population size and very limited distribution. Since the early 1970s, their population has hovered around 1,250-2,300 individuals and we have yet to see any increasing population trends.

[Fig. 4]

They were also listed because of the extremely high-risk threat of oil spills. The U.S Fish and Wildlife Service believe that oil spills will continue being the determining factor on whether or not sea otters will survive in California. Oil spills are detrimental to sea otter populations because the oil negatively interacts with their fur’s insulating properties, leading to hypothermia and death. There is only a 50% survival rate for animals that come into contact with oil so another accident like Exxon Valdez could wipe out the entire population. Other main threats to their existence include shark attacks, human interaction, and diseases. Human interactions include hunting, harassment, by catch through entanglement in fishing gear, and boating accidents. Diseases range from increased immune deficiencies due to low genetic diversity to increased parasite and pathogen exposure. 

[Fig. 5]

Description of recovery plan - A southern sea otter recovery plan was created in 1982. The goal is to, “establish the long-term viability of the southern sea otter population sufficiently to allow delisting the species”. The primary objective of the recovery plan is to create optimal environmental conditions that would allow the species to increase in numbers and range distribution. In order to be delisted, the southern sea otters would have to reach an average of 3,090 individuals or more for three years in a row. This can be done through more regulation of coastal vessel traffic (to decrease the risk of accidents) and continued efforts against oil spills (to reduce likeliness and impacts of more occurring). 

What Can You Do? - The general public can make a difference in the survival of the southern sea otter! The easiest and most important way is to cut down on consumption of oil and oil-based products. Plastic is an oil-based product so use more paper or reusable bags while at the store and around town. Dispose of all cooking oils and car oils properly otherwise they go straight into the ocean. Protesting oil drills is also another great way to create public awareness about wildlife being harmed as a result of human consumption. Check out these sites if you want to become even more aware of what is happening to wildlife around the world! 

U.S. Fish & Wildlife Service - https://www.fws.gov/ventura/endangered/species/info/sso.html

NOAA - http://www.noaa.gov/

References -

[Fig. 1] : http://2.bp.blogspot.com/-

LAXxyL65Bto/T7ciGWuqwNI/AAAAAAAAKzw/6U2CrnPIyFA/s1600/Funny+Sea+Otter_3.jpg

[Fig. 2] :- http://www.vanaqua.org/files/1013/2018/0738/otter-eat.jpg

[Fig. 3] : https://sanctuarysimon.org/regional_images/site_build/special_spp_otter_fig1.gif

[Fig. 4] : http://cdn.lifedaily.com/wp-content/uploads/2016/02/10-exxon-valdez-oil-spill-photo.jpg

[Fig. 5] : https://i.pinimg.com/736x/8c/18/64/8c18643f2f16e603e64ec1eba6906912.jpg