16 August 2016

Sea otters beyond utter cuteness

On the left are sea otters from ©Finding Dory and opposite is its real-life counterpart, Enhydra lutris (photo by Michael Gore).

Sea otters or Enhydra lutris are nearshore marine mammals, strongly associated with rocky coastal areas near kelp beds where they forage. Other than for food, they also use these kelp to sometimes entangle themselves with, keeping them afloat [1]. Most of time they are seen in groups called rafts [8], lying on their backs with such a laid-back pose [2], holding on to each other to make sure no one drifts away in their sleep [9]. They currently inhabit the coasts of Japan, Russia, Canada, North America and Mexico [1], but the majority reside in Alaskan waters [4].

True to being so adorable and a favorite in Finding Dory, sea otters are rarely seen fighting or being aggressive with their kin. In fact, they are weakly territorial, where only adult males form turfs [1]. 

Beyond being fuzzballs, what sets them apart from other marine mammals is their unique capacity to use tools. Using their forearms to grab a stone and prey from the ocean floor, they resurface to set a prey, for example, a mussel or clam on its chest, pries it open or smashes it against a stone [2]. Known as voracious feeders, sea otters even have pouches of loose skin under each forearm, where they could easily stash their prey [5]. They also feast on a variety of organisms such as sea urchins, crabs, squids, bony fish [3] and octopuses [6].

Unlike other marine mammals, they don’t have a thick layer of blubber to keep them warm. To compensate for this, they don the thickest and densest of furs, where a square inch of its skin can grow a million hair! [4]. To further keep the warmth, they spend hours grooming their coats until they are covered with natural oils [5]. They also eat to their tummy’s content (approximately 25% of their body weight), and spend most of their time resting afloat [4]. 

Below is a video of an Alaskan sea otter pup floating on its own [7].

It might not be obvious with how sea otters behave and handle themselves, but they are, most importantly, keystone species. That means their existence or absence has a greater effect in the ecosystem relative to other species. That is, sea otters help keep sea urchin population in check, and in turn maintain a healthy kelp forest [4].

Sea otters have been considered endangered since 2000 [1]. Today there are only about 100,000 to 150,000 individuals [2].

To know more about Enhydra lutris and other characters from Finding Dory, visit SeaLifeBase.

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[1] Doroff, A. & Burdin, A. 2015. Enhydra lutris. The IUCN Red List of Threatened Species 2015: e.T7750A21939518. http://dx.doi.org/10.2305/IUCN.UK.2015-2.RLTS.T7750A21939518.en. Downloaded on 26 July 2016.
[2] National Geographic (2016). Sea otter - Enhydra lutris. Retrieved from http://animals.nationalgeographic.com/animals/mammals/sea-otter/
[3] Gaichas, S. K. (2006). Development and application of ecosystem models to support fishery sustainability: A case study for the Gulf of Alaska. Retrieved from Proquest Dissertations and Theses database.
[4] Defenders of Wildlife (2016). Basic facts about sea otters. Retrieved from http://www.defenders.org/sea-otter/basic-facts
[5] Monterey Bay Aquarium (2016). Southern sea otter. Retrieved from https://www.montereybayaquarium.org/animal-guide/marine-mammals/southern-sea-otter
[6] Vincent, T. L. S., Scheel, D., & Hough, K. R. (1998). Some aspects of diet and foraging behavior of Octopus dofleini (W├╝lker, 1910) in its Northernmost Range. Retrieved from http://onlinelibrary.wiley.com/doi/10.1111/j.1439-0485.1998.tb00450.x/abstract
[7] BBC (2015, January 28). Sea otter pup left to float alone - Alaska: Earth's frozen kingdom: episode 1 preview - BBC two [Video file]. Retrieved from https://www.youtube.com/watch?v=sWJXG2SS6AA
[8] World Wildlife Fund (2016). Ten facts about sea otters. Retrieved from http://www.worldwildlife.org/blogs/good-nature-travel/posts/ten-facts-about-sea-otters
[9] Schweig, S. V. (2016, April 13). Sea otters hold hands while they're sleeping. The Dodo. Retrieved from https://www.thedodo.com/sea-otters-hold-hands-1727255897.html