Sea Otters: Adorable, Endangered, and A Keystone Species

Here_I_am.. sea otter baby sea otter

This cuddly creature is a sea otter, or Enhydra lutris, a well-known marine mammal native to the coasts of the northern and eastern North Pacific Ocean.  This furry, playful fellow is more than just adorable, however.  Otters are a keystone species.

In architecture, the keystone at the top of an arch holds the arch together.  Without the keystone, the whole arch and building surrounding it will collapse.  Similarly, some species of animals are called “keystone species,” meaning that a whole ecosystem, or interplay between living organisms and their surroundings, depends on that particular species to keep it running smoothly.

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Sea otters play a crucial role in their watery home.  How do we know?  Here’s the story:

In the 1700s, sea otters along the coast of California were hunted nearly to extinction for their furs and killed by fishermen who thought they were eating too much of the fish they wanted to catch.  When the otters disappeared, the animals they normally eat, sea urchins, enjoyed a large population boom.  Soon, there were so many sea urchins that they ate all of the kelp, a type of seaweed, at the bottom of the ocean, and caused an “urchin barren” to form, which means that the ocean floor is scraped clean and becomes an “ocean desert” in the ocean that is essentially devoid of life.  This is bad!  Fish raise their young in the protection of the kelp and other animals hide it in to avoid prey, and all those animals began to flee the scene as well. The fishermen now had less fish to catch, not more.  It turns out the otter was playing a much more crucial role in this ecosystem than people previously knew.

What happened to the otters?  In 1911, a treaty was passed to protect the sea otters from being hunted.  In some places, the populations of sea otters recovered, and eventually so did the kelp and fish.  But there are still some areas that have suffered near-permanent damage from the removal of just one type of animal – the sea otter – from its home.

Now, the sea otter is globally an endangered species, meaning that its numbers are so low that it is under imminent threat of becoming extinct, or dying out entirely.  The sea otter’s story shows us that if we take action we can achieve a remarkable success story that seems daunting, if not impossible, at first.

Sources:

“Here I am..” Top left photograph.  Photograph taken by Alan  Wolf and distributed under a Creative Commons License: CC BY-NC-SA 2.0

Baby sea otter photograph: sflo1822 on tumblr.

Three otters photograph: jamoore52 on tumblr.

Seat otter:  http://en.wikipedia.org/wiki/Sea_otter

Keystone species (definition): http://animals.about.com/od/animalswildlife101/f/keystonespecies.htm

Keystone species hypothesis: http://www.washington.edu/research/pathbreakers/1969g.html

Keystone species empirical evidence:  http://rspb.royalsocietypublishing.org/content/early/2012/07/03/rspb.2012.0856.full

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