Sea Otters and Their Drinking Behavior (They Have Large, Specialized Kidneys!)

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Published on October 4, 2022
Last Updated on October 12, 2023

You might ask yourself if an animal living in a water habitat ever gets thirsty. Being surrounded by vast, open waters must make drinking water convenient for marine mammals, right?

We must remember, however, that the ocean and seas where mammals like the furry sea otters live are made up of salt water. For humans, consuming too much salt will increase your blood pressure and may even earn you a trip to your general practitioner.

So how does a sea otter adapt to its marine environment? What do they drink if they get thirsty? And do they also consume other liquids aside from water? So please sit back and take a sip of your favorite beverage as we answer these questions and offer a toast to these fantastic sea otters.

Do Sea Otters Drink Sea Water?

Yes, sea otters drink the saltwater in the oceans and seas, like this fluffy one right here:

Marine mammals can get salt water from the prey they consume, or they can directly drink water from the ocean. 

Seals, sea lions, and manatees occasionally drink salt water. Yet they will look for fresh water and even snow to quench their thirst when they’re available. 

But unlike these fellow sea-dwellers, sea otters regularly drink seawater. 

How Can Sea Otters Drink Salt Water?

Sea otters can drink salt water because of their large, highly-specialized kidneys

Like most mammals, they have a pair of multilobulated kidneys. These organs appear like “packs of grapes”. Each “grape” or lobule contains nephrons which are the functional units of the kidneys.

Kidneys remove waste and extra fluid that mammals’ bodies don’t need. In marine mammals, like sea otters, their kidneys can extract fresh water from the salt water that they drink. It ensures that their bodies stay hydrated and functioning well despite living in the salty ocean. 

Sea Otters Have The Largest Kidneys Among Marine Mammals

Having large kidneys appear to be a requirement for mammals to live in a marine environment. 

When we compare the sea otters’ kidneys with respect to their body mass, reaching up to 100 pounds, they have the largest kidneys among marine mammals!

Specifically, sea otters’ kidneys comprise 2.01% of their body weight.

On the other hand, the kidneys of dolphins and whales (cetaceans) only account for 0.44 to 1.1% of their bodies. 

Also, the kidneys of their closest relatives, the river otters, weigh less than half of theirs, with 0.85%. So it indicates that the sea otters’ kidneys have adapted from their ancestors’ earlier freshwater environment to the fully marine one they have today. 

We can consider sea otters as fully aquatic marine mammals with these numbers alone! 

Marine MammalBody MassBody Weight % of Its Kidneys
Sea Otter100 pounds2.01%
Cetaceans (Dolphins and Whales)90 pounds and 300 pounds (smallest species)0.44 to 1.1%
River Otters31 pounds0.85%

Sea Otters Have Kidneys That Can Tolerate High Salt Intake 

Sea otters can remove excess salts in their bodies by excreting highly concentrated urine through their kidneys. They can even eliminate salt concentrations above the normal levels of seawater!

The body’s excretory or urinary system regulates body fluids through the kidneys. It removes extra fluid, salts, and nitrogenous wastes like urea from the blood. These wastes get excreted out of the body through urine

Here’s a video on how the kidneys work, albeit in humans for this instance:

Extreme amounts of sodium or salt in the body can cause the internal organs to go haywire and the body fluids to be unbalanced. Most mammals can only take in so much sodium before they develop a problem excreting salt from their bodies. 

Sea otters tolerate salt much better than most marine mammals. They can even excrete moderate to extremely salt-concentrated urine that maintains their kidneys’ health and incredible work.   

This marine adaptation also makes it possible for sea otters to drink seawater and not lose fresh water. Before the kidneys produce urine, they filter and reabsorb essential body fluids back into the body. For this instance, water goes back into the bloodstream while the excess salt gets discarded as waste

Sea otters can, therefore, handle ingesting high concentrations of salt in seawater. If humans had done that, they would’ve quickly become dehydrated by the overwhelming salt buildup.

Will Sea Otters Seek Out Fresh Water To Drink?

Yes, sea otters do seek out fresh water to drink!

In fact, caretakers and trainers have seen rescued and captive sea otters drink from unusual sources at Monterey Bay Aquarium.

They sometimes observed the sea otters trying to satisfy their thirst from water trickling through a garden hose.

In other instances, some otters were even trying to lick the freshwater that was cleaning the big exhibit windows via the aquarium’s sprinklers!

Would It Be A Good Idea To Leave Out Fresh Water For Sea Otters?

We at Floofmania think it’s a good idea to leave fresh water out for sea otters.

Since they already seek out fresh water, as mentioned above, it’ll be a treat for them if you make the water accessible for them to consume.

Researchers from Seattle Woodland Park Zoo have actually practiced this in the mid-90s. They provided a gallon of fresh water daily to three captive sea otters.

The otters seemed fulfilled by drinking the water because they would burp or rumble belch after their stomachs were full! 

Alternatively, they would also give snowballs to the sea otters. The researchers observed the otters hold the snowballs in their paws so they wouldn’t slip as they chewed on them. Each sea otter was reportedly able to consume two baseball-sized snowballs at a time!  

We might get a glimpse of how the sea otters enjoy eating snowballs through another sea otter group here. Some of them even manage to form snowballs themselves!

The Sea Otter Mostly Gets Hydrated By The Prey It Eats

Although most scientists say that sea otters get their much-needed water from the prey they consume, Mr. Daniel Costa thinks otherwise. He states that while harbor seals, dolphins, sea lions, fur seals, and porpoises can incidentally ingest saltwater while eating, sea otters mostly don’t.

When we think about it, the mentioned marine mammals usually eat their prey immediately underwater. But on the other hand, sea otters are known to bring their catch back to the surface to consume and crack hard shells In their “tummy tables”

The Sea Otters’ High Salt Content Invertebrate Diet Makes Them More Thirsty!

Sea otters need to consume a quarter of their weight in a day. As a result, they like to eat salty and protein-rich sea urchins, crabs, and abalones. Some of these crustaceans and mollusks might even have similar salt content to seawater.

But as we said earlier, sea otters can ingest seawater much saltier than the ocean. So they won’t have much of a problem consuming these food sources.

Once the sea otters eat their prey and their blood gets filtered by the kidneys, we can expect a massive amount of salt and also nitrogenous waste (urea).

Urea is the end-product of digesting and breaking down proteins (meat and shellfish, to name a few). Thankfully, this nitrogenous waste only takes a few gulps of water to be flushed out of the body as urine. 

And because the sea otters’ urine is highly concentrated, they will mostly excrete urea only and not much water. Their bodies need to conserve as much fresh water as possible, filtered from salt water, to remain hydrated.

While sea otters can also get some fluids from their prey’s juices, they still need more water to hasten the process and fulfill their daily metabolic needs.

In fact, sea otters are the only marine mammals that actively drink ocean water. And they do it to eliminate the high urea-nitrogen load in their urine. The more water they consume, the more urea is excreted in their urine.

Do Sea Otters Drink Other Liquids Than Water?

Yes, young and newborn pups feed on their mothers’ milk. But, in another scenario, some juvenile sea otters might have gotten too thirsty at the aquarium and drank their own urine!

Sea Otter Pups Need Their Mothers’ Milk

A sea otter pup consumes its mother’s milk from birth to about 6 to 8 months. 

The pup nurses from its mother’s abdominal nipples while lying belly down on its mother’s belly. The sea otter mom’s milk comprises 20 to 25% fat, an important energy source for a growing sea otter pup! 

Baby Sea Otters Sometimes Drink Their Urine!

Interestingly, a few juvenile sea otters at Monterey Bay Aquarium drank their urine for a few instances.

The staff from the aquarium noticed and noted their quite unusual behavior. The aquarium also didn’t provide any explanation or theories about the behavior. Perhaps the sea otters just got too thirsty and didn’t find any other water alternatives at the time. 

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!


  • 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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