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Do Whales Drink Seawater?

All mammals must drink water, and whales are no exception. You might wonder how they drink without so much salt in the water without getting ill. Whales cannot drink fresh water, as they are surrounded by water with a high salt concentration.

Whales get most of the water their bodies need from fish but can drink seawater as their kidneys have adapted to filter most of the salt. 

This is a fascinating topic, so if you want to know more, please read on.


Do Whales Drink Water?

Marine mammals do not drink water as land animals would. Marine mammals get their intake of water from what they eat.

In most cases, marine mammals, including whales, do not directly drink water from the sea. Water is supplied through the protein and fat from the fish they eat.

The amount of water they need depends on what species of fish they eat. Some species of fish have more water in them than others.

A pregnant whale typically feeds on different fish than a non-pregnant whale. A pregnant whale feeds on fish with higher protein and fat to feed the calf growing inside them. 

After the calf is born, the female changes their diet to a fish with higher water content. This allows them to produce milk for the calf. All fish provide sources of water.

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

The blue whale takes 10,000 gallons of water into its mouth while eating. However, they do not drink that water but will swallow small amounts when swallowing food. The baleen whale’s mouth filters the food through the baleen and then pushes most of the water out. 

Whales need less water than other mammals as they live in the ocean. They lose less water to their surroundings compared to land mammals. Whales don’t sweat as other land mammals do and lose less water from their bodies. 

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Do Whales Drink Sea Water?

Studies have shown that whales drink 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 whales drink some seawater because the salt is excreted in their urine. Their urine contains more salt than seawater. The urine of a whale is primarily composed of sodium. 

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Gray whale

How Do Whales Filter Salt out of Saltwater?

Whales drink salt water, which means they have a high sodium concentration. This is unhealthy and can lead to severe hydration and death. Whales have massive kidneys, and their efficiency allows the whale to filter out 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. 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 salt while retaining the amount needed. 

Measuring the amount of salt excreted is difficult, but their urine holds the answer. It has been found that whale urine has more salt than the water they drink. The urine is ten times as salty as their blood. 

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How Does A Whales Kidney Function?

A whale’s kidney is built to regulate the salt they take in through seawater. Many marine mammals, such as whales, seals, and sea lions, are well adapted to their environments. They live in salty water and have no other option but to drink salt water when feeding.  

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

These differences indicate 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. A whale’s kidney has the increased thickness necessary to produce highly concentrated urine.

Whales have multi-lobed kidneys. 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 salt balance.

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How Do Whales Ingest Water?

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

Whales also drink seawater but only occasionally and use their large kidneys 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 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 drunk. 

Do Whales Get Thirsty?

Although whales live in an aquatic environment and never leave it, research suggests that they can become dehydrated in some circumstances. If a whale has been swimming long distances or engaging in strenuous activity such as breaching or tail slapping, their body may lose water and become dehydrated. 

In these cases, whales would likely need to consume water to replenish their bodies. Whales living in warmer climates may also experience thirst due to the higher temperatures, which can cause dehydration. Despite not being able to drink ocean water directly, whales can quench their thirst by consuming small prey items such as krill and squid, which contain high moisture levels, and taking in small amounts of saltwater which they filter through their kidneys.

How Do Other Marine Mammals Filter Salt?

Marine animals, such as dolphins and seals, use a process known as salt gland filtration to filter salt from their bodies. The process entails the secretion of a special fluid known as nasal mucus, which contains enzymes that break down the concentrated salt solution in seawater.  This fluid is then passed over specialized cells located within the mammal’s nasal cavity, which act as a filter. The filtered fluid is then secreted out of the nostrils and onto the skin, where it evaporates, removing excess salts from the body. This process helps marine mammals maintain an appropriate balance of electrolytes in their bodies while they are swimming in salty waters.

References and Further Reading

The Natural History of Whales and Dolphins” by Richard C. Connor and D.W. Rice

“Whales and Dolphins: Cognition, Culture, Conservation, and Human Perceptions” edited by J.G. Mead and R.W. Osborne

“The Encylopedia of Marine Mammals” edited by Bernd Würsig, J.G.M. Thewissen and Kit M. Kovacs

“Cetacean Societies: Field Studies of Dolphins and Whales” edited by J. Mann, R.C. Connor, P.L. Tyack and H. Whitehead

“Marine Mammals: Evolutionary Biology” by Annalisa Berta, James Sumich, and Kit Kovacs

UCSB Scienceline

Journal of experimental biology