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Do Whales Drink Seawater?

Whales live in water, and like all mammals must drink water to survive.  With so much salt in the water, you might be wondering how they manage to drink seawater without getting ill.

Whales do drink seawater, as their kidneys have adapted to filter out a lot of the salt. However, whales get most of their water intake from their diet of fish. 

If you want to know more information then please read on.

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Do Whales Drink Water?

In most cases, marine mammals such as whales do not directly drink water from the sea. Water is supplied through the metabolism of protein from the prey and the oxidation of fat. 

This means that marine animals do not drink water as a land animal would. Marine mammals get their intake of water through their food.

The amount of water they intake depends on what species of fish they feed on. Some species of fish have more water in them than other species.

A female whale, when pregnant, typically feeds on different species of fish than a non-pregnant whale would. A pregnant whale would feed on fish with a high amount of protein and fat for the calf growing inside of them. 

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After the calf is born, the female whale tends to change its diet to a fish with higher water content. This food allows the whale to be able to produce milk for the calf. All species of fish will provide some water as part of the whale’s diet.


Whales live and spend all their time in seawater. The whale’s bodies need water to survive, and scientists assume that whales do drink some seawater.

The blue whale takes up to 10,000 gallons of water into the mouth while eating. However, they do not drink all of that water but will swallow small amounts. 

The baleen whale’s mouth filters the food through the baleen and then pushes the water out, but it will still take some seawater down. 

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Whales need less water than other mammals need as they live in an environment surrounded by water. Because of this, they lose less water to their surroundings compared to land mammals. Whales do not sweat as other land mammals do. Thus they will lose less water from their bodies. 

Do Whales Drink Sea Water?

Whether whales drink seawater is one of the questions that scientists have tried to tackle over the years.

There is one conclusion that whales do take in seawater but only in small quantities. This conclusion is anchored to tests on whales’ urine concentration.

Whales produce urine with an osmolality higher than seawater. Osmolality tests how much substances such as sea salt have dissolved in urine. There is an interesting article from the Journal of Experimental Biology, which you can find here.

It is believed that marine mammals such as whales drink seawater because their urine contains more salt than seawater. It is assumed that the urine of a whale is primarily composed of sodium. 

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How Do Whales Filter Salt out of Seawater?

Whales take in seawater, and this means they have a high sodium concentration. When you drink salt water, it means you are receiving high levels of sodium into the body.  

Gray whale

This is not healthy and will lead to severe hydration and can result in death. Due to the whale’s kidneys’ massive size, their efficiency allows the whale to filter out the salt without sacrificing the water their bodies require. 

Scientists believe that whales filter salt water from their bodies. They do this by reabsorbing more water into the kidneys.

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The studies on salt urine concentration tell us that whales filter seawater after taking it into the body. Whales use their large kidneys to process and excrete the extra amount of salt while retaining the maximum amount of salt needed. 

It is not easy to measure the amount of salt excreted, but their urine holds the answer. It has been found that whale urine has a higher amount of salt than the water they drink. The urine is ten times as salty as their blood. 

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How Does the Kidney Function of a Whale?

The kidney of a whale is built to regulate the salt they take in through the seawater. Marine mammals such as whales are well adapted to their environments. They live in salty water and have no other option but to drink some saltwater when feeding.  

Whales can succeed in this environment as their kidney structure is unique. Some differences exist between the kidneys of a marine and terrestrial mammal.  

These differences are an indication that their specialized kidney allows them to occupy habitats with a broad range of salinity.

The kidney is the principal organ of water and electrolyte regulation.  The kidney of a whale has increased thickness necessary to produce highly concentrated urine. This is important for mammals such as whales living in a hyperosmotic environment. 

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Whales have a multi-lobed kidney. The kidney has an increased surface area for removing toxins from the body more efficiently than a non-lobed kidney.  

Whales typically regulate their water balance by metabolism and only drink seawater occasionally to maintain the balance of salt in their bodies.

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How Do Whales Ingest Water?

Water is essential to any living thing and is just as important to whales. They acquire water from the food they eat after metabolism takes place. Whales chose what to eat to ensure they get enough water from their food. 

Whales also drink seawater but only occasionally. They have a large kidney to remove the salt from the water.

Researchers can measure the amount of seawater ingested by organisms using isotopic tracers. These tracers are atoms that are introduced or already present in water. These atoms can be differentiated and detected due to their mass. 

Researchers add the amount of water ingested by food intake and metabolism to compare the amount of total water passed into the body. The difference between the two quantities gives them a good indication of the seawater’s amount that a whale has ingested. 

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Whales breathe through a blowhole while they eat through the mouth. The separation helps whales not to consume water, which can accidentally enter into their lungs when consuming prey. 

In conclusion, whales need water to survive. Therefore they can drink seawater. Their large kidney can filter salt after drinking in the water. The filtration system is more advanced in whales than land mammals due to their multi-lobed kidney/.  

Whales also get their water from their prey. Whales have adapted to know which fish give them the water they require. Whales also do not require as much water as other humans beings do, due to their lack of sweating. 

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UCSB Scienceline

Journal of experimental biology

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