Enhydra lutris, commonly known as the sea otter, is currently categorized as endangered under the IUCN Red List of Threatened Species (Larson et al., 2020). The sea otter is the smallest marine mammal, and unlike most other marine mammals it shares its environment with, such as sirenians and cetaceans, this mammal retains its fur in its frigid marine environment (Kenyon, 1975). The result is the densest coat of any mammal on earth having approximately 130,000 hairs/cm² (Yochem & Stewart, 2009). Unfortunately, this incredible adaptation meant to protect them from the freezing waters of the Northern and Eastern Pacific Ocean made them a prime target of the fur industry, and in the 18th and 19th century, the maritime fur trade razed their populations to near-extinction (Loshbaugh, 2022).

There are currently more than 41,000 species on the IUCN Red List that are under threat of extinction (IUCN 2022). What is so special about this one? The sea otter is a keystone species. This means that the effect of these animals is disproportionately large relative to the abundance of the species. We've witnessed this before. When they were overhunted for fur, their population was extirpated from certain kelp forest ecosystems (Davic, 2003). As the main predator of sea urchins, when the otters vanished they overpopulated and quickly took over these ecosystems. This wreaked havoc on the entire ecosystem; the kelp that built the ecosystem was replaced by "urchin barrens" (Stewart & Konar, 2012). Thousands of marine organisms rely on the kelp forests to survive. Kelp is a food source and shelter for many animals and absorbs large quantities of carbon dioxide. When the animals that hide in kelp have no kelp to hide in, they are exposed and killed. When the animals that eat the kelp have no kelp to consume, they die (Power et al., 1996). The predators of said animals, such as bald eagles, have a huge loss in the abundance of prey available and also go hungry. The ecosystem collapses, this is called trophic cascade (Anthony et al., 2008). The existence of countless other species rely on the continued existence of the sea otter. This marine mammal may be small, but the effects it has are huge.

References:

Doroff, A., Burdin, A. & Larson, S. 2021. Enhydra lutris. The IUCN Red List of Threatened Species 2021: e.T7750A164576728. https://dx.doi.org/10.2305/IUCN.UK.2021-3.RLTS.T7750A164576728.en. Accessed on 19 November 2022.

Kenyon, K. W. (1975). The sea otter in the eastern Pacific Ocean (First American Edition). Dover Publications.

Yochem, P. K., & Stewart, B. S. (2009). Hair and Fur. Encyclopedia of Marine Mammals, 529–530. https://doi.org/10.1016/b978-0-12-373553-9.00124-3

IUCN. 2022. The IUCN Red List of Threatened Species. Version 2022-1. https://www.iucnredlist.org. Accessed on 19 November 2022.

Mary E. Power, David Tilman, James A. Estes, Bruce A. Menge, William J. Bond, L. Scott Mills, Gretchen Daily, Juan Carlos Castilla, Jane Lubchenco, Robert T. Paine, Challenges in the Quest for Keystones: Identifying keystone species is difficult—but essential to understanding how loss of species will affect ecosystems, BioScience, Volume 46, Issue 8, September 1996, Pages 609–620, https://doi.org/10.2307/1312990

Anthony, R.G., Estes, J.A., Ricca, M.A., Miles, A.K. and Forsman, E.D. (2008), BALD EAGLES AND SEA OTTERS IN THE ALEUTIAN ARCHIPELAGO: INDIRECT EFFECTS OF TROPHIC CASCADES. Ecology, 89: 2725-2735. https://doi.org/10.1890/07-1818.1

Loshbaugh, S. (2022). Sea Otters and the Maritime Fur Trade. In Ethology and behavioral ecology of sea otters and polar bears (pp. 173–204). essay, SPRINGER NATURE.

Davic, R. D. 2003. Linking keystone species and functional groups: a new operational definition of the keystone species concept. Conservation Ecology 7(1): r11. [online] URL: http://www.consecol.org/vol7/iss1/resp11/

Stewart, N. L., & Konar, B. (2012). Kelp forests versus Urchin Barrens: Alternate stable states and their effect on sea otter prey quality in the Aleutian Islands. Journal of Marine Biology, 2012, 1–12. https://doi.org/10.1155/2012/492308

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