The Sea Otter’s Foraging Behavior (They’re Picky, and They Use Tools!)

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Last Updated on September 2, 2022 by Tommy

Sea otters are the only fully aquatic otter species and the only living members of the Enhydra genus. They are arguably the cutest shallow coastal water dwellers in the animal world – scientifically speaking, of course, ahem.

These adorable marine mammals are diurnal. They forage for their food before sunrise and go for another round just before the sun sets. These searches for prey take dedication and hard work, so they need to rest at night and get some naps in the middle of the day while holding each other’s paws and forming rafts. 

Do you want to know what these sea otters’ diets consist of and how they hunt for food? The rest of the article will look closely at how a sea otter serves its favorite meal fresh on the table. 

Sea Otters Eat Mostly Shellfish, Clams, and Aquatic Invertebrates

There are about a hundred options for sea otters to prey on, although they actually choose from 33 species. 

Surprisingly, each sea otter prefers 2 to 3 food options in their diet, usually consisting of benthic invertebrates like mussels, sea urchins, snails, and crabs. 

They then stick to their favorites for the rest of their lives!

Biologists believe this individualistic and highly specific meal preference was an evolutionary adaptation passed down for generations. Depending on the area and conditions, sea otter mothers perhaps taught their pups to favor the most abundant prey at that specific time. 

And sea otter moms can pass these preferences down to many family lines!

Why Don’t Sea Otters Hunt Moving Fish?

Sea otters can lose their body heat from swimming and living in a cold environment alone. Therefore, they need to keep their temperature at 100°F by burning calories while having a very fast metabolism. Phew.

Thus, these mammals need to consume a lot of food – a quarter of their weight daily to keep up and replenish energy stores. And the most efficient way to adapt to this is to keep the hunting grounds nearshore and choose accessible and slow-moving prey that put up almost no fight to conserve energy. 

So even though some sea otters, particularly the Northern subspecies, eat fish, they prefer the sluggish and bottom-dwelling species of Red Irish Lord and the pufferfish family. 

Furthermore, the sea otters’ dive in the water usually lasts only 1 to 5 minutes before they come up for air, so they generally swim less than 60 feet below rocky reefs and kelp forests.

How Do Sea Otters Find Their Prey?

Sea otters must primarily rely on their whiskers and forepaws (sense of touch) to find their prey underwater. 

These sea otters get their food from the ocean. As surface air breathers, they prepare to dive into the sea by taking in and holding in a deep breath. Then they close their nostrils and small ears before leaping into the water. 

Once underwater, the sea otters have to depend on their long, highly sensitive whiskers or vibrissae to locate a hidden crab or snail in dark or murky waters. They could also use their strong front paws to reach into crevices and turn stones over where limpets or chitons could be hiding. 

In fact, the sea otter is the only marine animal that can lift and flip rocks over using its forepaws when searching for its meal on the seafloor!

A sea otter’s forepaws are also powerful enough to dig in the nearshore sea floor for invertebrates like a clam that could bury itself up to 20 inches under the sand. In addition, their forearms are agile, and they can swiftly go through numerous kelp beds to find and grasp prey.  

These sea otters are the only marine mammals that use their front paws instead of their teeth to catch their prey!

How The Sea Otters’ Picky Eating Helps Kelp Forests

Aside from having a personal diet preference, these sea otters are also choosy in selecting their sea urchin prey in their role as keystone species.

Sea otters apparently prefer the big, healthy, and more nutritious sea urchins that feed on rich kelp growth areas. Biologists confirmed this behavior during the 2014 sea urchin outbreak in Monterey Bay, where they also dramatically increased their sea urchin consumption by up to 3X.

Herds of large sea urchins eventually create an “urchin barren” that mostly has no other living beings besides themselves when they completely eradicate kelp forests that are home to many aquatic species, especially juvenile fish. 

In the same study, researchers noticed that sea otters chose to ignore these urchin barrens where these sea urchins would have been plenty and laid out ripe for picking. Upon further studies, they found that these urchins were “zombie-like” – basically unhealthy and empty when they opened them up!

Hunting these nutritionless urchins is not worth the time and effort for the energy they would’ve wasted, which a sea otter’s body desperately needs to conserve. And it only shows just how intelligent sea otters are! 

Choosing to protect a healthy kelp forest, no matter how small the patch may be, increases kelp growth and distributes kelp spores that will restore the urchin-dominated kelp beds after some time. 

In addition, regardless of how voracious sea otters can get, they will never completely wipe out a species in an area. So sea otters would more likely leave babies or the smaller individuals of their prey behind to flourish.

How Do Sea Otters Get Into The Tough Shells?

According to a study by the Burke Museum, researchers found that a sea otter’s skull is short and blunt and equipped with a flat and fracture-resistant set of teeth capable of inflicting its prey with 80 pounds of bite force!

Specifically, a sea otter can effortlessly split the hard-to-crack shells of marine invertebrates using its four lower incisors. Their teeth also contain extra layers of protein-rich-gel enamel that can help prevent them from easily getting chipped and damaged.

However, even a mighty bite force could prove insufficient to shellfish with the heaviest armors or special skills. So sea otters had to learn to adapt to their prey and use tools.

Sea Otters Are Avid Tool Users

Sea otters are only one of the few marine mammals known to use tools such as rocks.

In fact, scientists believe that their ancestors have already been using stone tools long before other marine mammals for thousands or even millions of years. 

These intelligent otters usually use rocks either as hammers or anvils:

Rocks As Anvils

The most popular videos you would find online when searching for a sea otter enjoying its meal are the ones where the otter is floating on its back, pounding a sea urchin or crab against a rock lying on its chest or stomach.

Alternatively, a sea otter can repeatedly bash its prey against a fixed big stone or boulder until the shells of marine snails and bivalves like mussels and scallops crack open.

Rocks As Hammers

Sea otters famously use rocks as hammers when they pry an abalone off their rock habitat – and it has a gripping force of up to 4,000X its body weight!

So the patient otter must dive 2 to 3 times to completely bash the abalone away using a large stone at a fascinating rate of 45 blows in only 15 seconds!

Some otters can also smash snails and clams by directly hammering their shells away with a rock to get to their tasty insides.

Other Tools

As residents of kelp forests, sea otters can utilize the kelp fronds or blades by storing and hiding their extra catch for later. The kelp prevents their prey, like a crab, from escaping and keeps it afloat so they can savor it fresh for much later.

Apart from using rocks, the sea otters might also use their prey’s body part or another individual of the same species to break their shells away.

For example, the sea otter can take a claw of the crab apart from its body and hammer it against its shell. Or they pit a sea urchin against another urchin to get rid of their spines.

Do Sea Otters Keep A Preferred Rock With Them?

Rocks are essential for how these sea otters forage and eat their food, so carrying a favorite one wherever they go is reasonably necessary. 

Furthermore, a sea otter would not have favored a stone out of all the other available rocks on the ocean floor if it had not passed the rigorous qualifications that these sea otters have learned from their mothers. 

The stone should be big enough to act as an anvil but small enough to be hidden and tucked under a forearm’s pouch and be carried back to the surface.

How Does The Sea Otter’s Pocket Work?

Speaking of the forearm pouch…

Under each of the sea otter’s two front arms, a loose pouch or skin flap extends across its chest. 

These two pouches act as shopping bags where the sea otters can keep some of their catch inside while they search for other prey in the area. They also work as safe-keepers for every sea otter’s unique favorite rock.

Some even say that most otters prefer to store items in their left forearm pouch!

So, do you remember that sea otters can only dive from one to a few minutes? 

They must search for prey and tuck them inside their pouches quickly too. Then, they need to return to the surface for air, prepare for another dive, or immediately eat their fresh catch. 

Where Do Sea Otters Eat Their Food?

As air breathers, sea otters need to consume their prey on the ocean surface with their backs floating in the water and use their chests or stomachs as dining tables. 

While on their “table,” the sea otter can now fish out any stored food items in their underarm pouches and use their preferred rock to crack shellfish open if they’re on the menu.

They also frequently roll in the water to wash food scraps or debris away during or after a meal. 

So does the pun I made in the introduction of this article makes sense now? I hope you caught on to that one cause I had fun writing it!

How Do Sea Otters Avoid Getting Pinched By Crabs and Stung By Sea Urchins?

Apart from passing down food preferences and teaching their pups the right size of rock to use as a tool, getting unharmed while eating prey will still be credited to a sea otter’s dear mother. 

Sea otter moms teach their babies that in order to avoid getting pinched by a crab, they have to pull and eat its legs first, especially the claws. 

No pinchers, no pain indeed.

And a sea otter’s forearms are powerful, so they can easily twist and pull the crab’s legs away without a sweat.

In addition, their forepaws have retractable claws and rough pads, which are the features that will help them easily grasp slippery or spiny prey like a sea urchin. 

Once the sea otter breaks the prickly spines of the urchin with its paws, it then uses its teeth to chomp through the underside, where the remaining spines will be the shortest. The otter can now reach and enjoy the soft contents inside the shell. 

Do Sea Otters Hunt Alone?

Although sea otters nap and sleep together while holding each other’s paws that form single-sex rafts, every adult and independent pup forage alone. 

Sea otters are never truly social animals, even though they can play and bond with each other. Each adult otter is fully capable of hunting, grooming, and even defending itself. 

Are Sea Otters Very Protective Of Their Food?

Sea otters are generally peace-loving mammals that scientists rarely observe fighting in their population.

More often than not, if another sea otter from the group decides to help itself to some food from its friend’s tummy table, the victim will most likely not react at all but simply go down for another helping!

On top of that, sea otters have individual food preferences that may be similar to their group but still avoids competition with one another.

What Do Sea Otter Moms Do With Their Babies While Foraging For Food?

A sea otter baby is born with a buoyant thick coat of baby fur or lanugo, so these pups can’t swim or dive for food and just delightfully bob on the water surface. 

Hence, a sea otter mom will usually wrap and tuck their pups in kelp to prevent them from floating away on the ocean when she’s out to hunt for food for both of them.

Alternatively, some mothers may hoist their babies on boat decks or docks while they forage. Swimming and diving lessons from mom don’t start until they’re four weeks old. Sea otter pups will continually learn their mothers’ hunting preferences and survival techniques until they’re eight months old.

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Author: Gra

Hello! My name is Graciola Galo, but my friends call me “Gra” – so can you! Aside from being a dog lover, my bachelor’s degree in biology has helped me develop a deep appreciation for animals. I look forward to learning more about all kinds of wildlife in every future article I write for Floofmania and I aspire to impart that same awe and wonder to you, too!

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