Sea otters (Enhydra lutris) are native to the Pacific Coast and were once found all the way down into Baja California. Sea otters have been a coveted species dating back hundreds of years. This furry marine mammal has the densest fur in the animal kingdom, with approximately 1,000,000 hairs per square inch, versus the average human, with 20,000 hairs per square inch.

The Many Threats to Sea Otters

The fur from this animal was highly desirable and otters were extensively hunted between 1741 and 1911. Historic populations in California before hunting began were estimated to be 16,000. However, with the increase in commercial harvest between 1700 and 1900, Russian, Spanish, and indigenous explorers drove this species to near extinction. At the end of the fur trade in 1911, world otter populations bottomed out at 2,000 individuals.

After 1911, the otter had been reduced to 13 remnant populations. This has resulted in a low genetic diversity and can lead to breeding difficulties or trouble in sustaining viable populations. In addition to the resulting low genetic diversity, otters also face threats from oil spills, diseases, and conflicts with fisheries. Oil spills are a problem because, once the otter’s fur is covered in oil, its ability to insulate the body is compromised, ultimately causing hypothermia and death. Another threat to otter populations includes diseases from parasites, especially Toxoplasma gondii, which appears in cat feces. The feces contaminate sewage, which then drains into the ocean and pollutes local waters.

Another major threat to otters is competition with fisheries for seafood resources. Fisheries are opposed to increasing otter habitat because they pose an economic threat to shellfish stocks. Otters are blamed for the decline of seafood resources, but this decrease is likely due to human mismanagement and overharvesting.

Legal Measures to Protect Sea Otters

To combat these threats, many legal measures have been taken. In 1910, the United States, Great Britain, Russia, and Spain all signed a treaty to ban the hunting of otters. It is illegal to hunt sea otters today, but pelts are still sold on the black market. Other legal protections include listing under the Federal Endangered Species Act in 1973 and the Marine Mammal Protection Act of 1972. Another attempt to increase otter populations includes the establishment of marine protected areas. These are areas where harmful activities to marine life are prohibited. The Monterey Bay National Marine Sanctuary is one such area, and it is home to an estimated 1,200 otters. These legal actions have resulted in an overall population increase and have allowed the sea otter to successfully return to 2/3 of its historic range.

Sources

Doroff, A. & Burdin, A. 2013. Enhydra lutris. The IUCN Red List of Threatened Species. Version 2014.3. Web. Accessed 10 February 2015. http://www.iucnredlist.org

Natural Resources Defense Council. 2001. Southern Sea Otter. The Green Gate: NRDC’s Environmental Guide to the San Francisco Bay Area. Web. Accessed 10 February 2015. http://www.nrdc.org/greengate/wildlife/otterf.asp

Miller MA, Kudela RM, Mekebri A, Crane D, Oates SC, et al. (2010) Evidence for a Novel Marine Harmful Algal Bloom: Cyanotoxin (Microcystin) Transfer from Land to Sea Otters. PLoS ONE 5(9): e12576. doi:10.1371/journal.pone.0012576

Sea Otter. Edited 28 January 2015. Accessed 10 February 2015. http://en.wikipedia.org/wiki/Sea_otter

"Sea Otters, Enhydra lutris." MarineBio Conservation Society. Web. Accessed Wednesday, February 11, 2015. Last update: 1/14/2013 2:22:00 PM. http://marinebio.org/species.asp?id=157