Tag Archives: Keystone Species

Why Are You so Fluffy Sea Otter?

Have you ever looked at a dog and thought boy that thing sure does look fluffy? Well image petting that puppy and it just feeling like a big ole fluffy pillow… so fuzzy and warm. Now take that fluffy and that warmth and multiple it by 1 MILLION!!! and you got yourself a Sea Otter.

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Southern Sea Otter Enhydra lutris 6-8 week old pup in rehabilitation feeding from bottle Monterey Bay Aquarium, Monterey, CA

            The sea otter has the densest fur out of any mammal on the planet, exceeding upwards of 1 million hair follicles per square inch. That’s more hair per square inch than an entire German Shepard.

Not to be confused with the marine otter or the European otter, the Sea Otter is found along the west coast of North America, from Baja California all the way up to the icy waters of Alaska across the Pacific to the north of Japan. In comparison to its cousins the Sea Otter is the largest of the 3 different species. It ranges in size of approximately 4 feet 7 inches (female) to 4 feet 10 inches (males) and can weigh up to 100 lbs., probably a lot bigger than you guessed. Sea otters can also live to be about 20 years old. They have long streamline bodies that is almost entirely covered in very dense fur, the only part of its body that isn’t covers in fur are its pad. Their pads are on the bottom of their paws and the tips of their nose.

Well these little fur balls need to eat something right? A sea otter typically likes to hangout in kelp patches and rocky areas where they can dive down and pry smaller invertebrates off the rocks such as lobsters, crabs, snails, and their favorite snack, sea urchins. Once they have their tasty treat they will bring it to the surface and use their bellies as a table to hold onto the snack. Crabs, lobsters, and other inverts can have really dense and hard shells which can make it challenging for the otter to get to the meat, oh wait just kidding! Sea Otters have developed the ability to utilize rocks as tools to crack into the hard shells. Each sea otter has a unique rock that they will carry with them at all times, they have a loose patch of skin on one side of their chest (preferably their left side) that they will tuck the rock into and pull out when it’s time to munch down on dinner.

Sea Otter Dinner

After a long day of floating around and eating tasty invertebrates otters need to take a nap and catch up on some Z’s. In order to make sure that they don’t drift away in the waves a sea otter will actually wrap themselves in the kelp to tie themselves down or a group of otters might raft up together so they can stick together, typically in groups of 10 to 100, the largest every counted raft of otters was over 2000 strong, so many otters!!!

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Now that we know a little bit about these fuzzy Sea Otters, why are they so fluffy?

Sea otters have very thick dense fur for a couple of reasons. Sea otters although they do have legs and feet with the ability to walk on land they spend a majority of their life in the ocean rarely going to shore. Being in the water almost 24/7 it can get a little chilly out there, especially for those sea otters that make the islands of Alaska their home where water temperature can drop below 50 degrees Fahrenheit. By having such thick fur it allows them to stay incredibly warm and maintaining a constant internal body temperature, this process is known as thermoregulation. Sea otters actually spend a majority of their day grooming themselves, removing knots and tangles, squeezing out water, and removing and debris or dirt.

Sea otters are also a prime example of the importance of a keystone species, a keystone species is crucial for any ecosystem helping keep other organisms in check. Sea otters help keep the sea urchin population in check. Sea urchins are herbivorous inverts that like to go after the lower stock of kelp, in doing this it releases the kelp from its holdfast allowing to drift off into the open ocean and eventually dying. If this persists urchins can wipe out entire kelp forests which can have even more devastating effects.

Sea otter dinner

The Keystone Species

Keystone Species are those of any organism that are considered crucial to the structure of the ecosystems in which they belong. The sea otter is an excellent example of a keystone species for the kelp forest ecosystem off the coast of California. Keystone species are important because they help promote biodiversity by controlling species that would otherwise dominate the biological community in which they reside. Also, these species can provide essential resources to other species within the community. Many keystone species are predators like a jaguar, but not all, some are herbivores like the African elephants in the savanna ecosystem.

Without keystone species present, the ecosystems would become dramatically different and many other species could be lost.



The term keystone refers to the center stone of a bridge that is wedge shaped and helps hold the others in place. If this stone is removed the entire bridge should collapse in on itself. The same idea goes for an ecosystem that loses a keystone species. Keystone species are so vital to the communities in which they belong because they are the stone that maintains the structure and function.

Keystone Species

An American zoologist Robert Paine was the first to coin the term keystone species back in 1966. While studying the rocky intertidal ecosystem in the Pacific Northwest, Paine observed dramatic changes to the biological community when the Starfish (Piaster ochraceus) was removed.

Of course, one of the most popular examples of a keystone species is the sea otter (Enhydra lutris) within the kelp forest ecosystem. As a member of the weasel family, the sea otter does not posses insulation in the form of thick blubber as many other marine mammals do. Instead the sea otter has an extremely high metabolism and the densest fur of any animal on the planet! The sea otter has such an appetite; it must consume 25 percent of its own body weight daily! Sea otters may appear cute and cuddly to humans, but they are actually voracious predators keeping the populations of invertebrates like sea urchins in check. They provide balance in the kelp forest by controlling the populations of invertebrates that feed upon the kelp.

Keystone species otter


Unfortunately, Russian fur traders sought after the pelts of the sea otters along the pacific coast of North America throughout the 17 and 1800’s. Eventually traders diminished the otter populations to the brink of extinction. This decimation wasn’t just trouble for the otters, the productive kelp forest ecosystems were greatly affected.

The populations of urchins within the kelp forest ecosystem expanded without sea otters as predator to keep the urchins from overpopulating. Sea urchins graze on the holdfasts of the kelp, and if gone unregulated, they can wipe out whole forests because the kelp can no longer anchor itself and simply floats away. This process can create desolate urchin barrens in areas that were once productive kelp forests. It’s not just the kelp itself that is impacted; there are over 800 species that rely on the kelp for food and habitat. Once the kelp is gone many species disappear with it, thus providing evidence that the sea otter is a vital keystone species.

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keystone species urchin


Since the protection of sea otters, populations have increased in areas like Big Sur and Monterey Bay, California, but they still remain an endangered species. People are not sure if sea otter populations will ever fully recover, but hopefully we can learn from this important keystone species for future decisions facing ecosystems all over the world.

Written By: Chad Brewer

Keystone Species: Guardians of Ecosystems

The keystone of an arch is the center stone that holds the whole structure together. If that one stone is shifted, the entire archway will no longer be able to hold its shape. Similarly, a keystone species is a species that plays a very influential role in maintaining the balance of an ecosystem. If it is taken out of its environment, the ecosystem it leaves behind will take on a drastically different structure.

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A common example of a keystone species in the Pacific Northwest is the sea otter. Sea otters are marine mammals that feed on sea urchins, crabs, abalone, and other shelled animals. Because a sea urchin’s favorite foods are kelp holdfasts and other algae, it is important for their population levels to be regulated so overgrazing does not occur. As the primary predator of sea urchins, sea otters ensure that urchin population levels never get too high. However, sea otters have faced several obstacles to their survival over the years. Overhunting in the 1800s completely wiped out otter populations in Southern California, and today Northern California otters continue to face threats from fishing practices, pollution, and predatory changes. As sea otter populations continue to decrease in some areas, “urchin barrens” have been found dotting parts of the ocean floor. These are created when urchin populations get too high and start to eat every piece of algae in sight, taking down whole kelp forests in their search for more food. Without the kelp to hide in and feed on, fish move on to other places, leaving only a barren wasteland of hungry urchins behind. The habitat collapses when the sea otter is not there to maintain its healthy balance.

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The California Sheephead is a keystone species that stops urchin barrens from happening in the waters around Catalina. Just like otters, Sheephead’s love to feed on those algae-loving echinoderms. Their sharp teeth are perfectly suited to breaking through the urchin’s spines and hard exoskeleton. However, also like otters, the California Sheephead faces its own set of challenges for survival. Commercial and recreational fishing have given it a vulnerable population status, which has led to higher restrictions being placed in recent years on the size and amount of the fish that can be taken. Due to the important role it plays in Catalina’s ocean ecosystem, we can only hope that the California Sheephead continues to thrive in these waters for many years to come.



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