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All animals must drink water, and whales are no exception. Whales can only drink salt water as they do not have access to fresh water. Do you know how they survive without drinking fresh water?

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. 

Whales have some fantastic adaptations that allow them to survive without fresh water. Please read on to find out more.


Do Whales Drink Water?

Whales require water, yet their method of obtaining it differs from land animals. Marine mammals source their hydration primarily from their food rather than directly consuming water.

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 higher water content than others.

Pregnant whales feed on different fish than non-pregnant whales. They prefer 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 a higher water content. This allows them to produce milk for the calf. All fish provide sources of water, but not all provide the same amount.

Whales live and spend all their lives surrounded by water. Whales need water to survive, and scientists assume that they do drink seawater.

The blue whale takes in 10,000 gallons of water into its mouth while eating. However, they do not swallow all the water but will swallow small amounts when swallowing food. Baleen whales filter food through baleen plates and push most of the water back out into the ocean. 

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 and lose less water from their bodies than land mammals. 

Do you know how whales feed underwater? Find out here.

Do Whales Drink Seawater?

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 on this subject.

It is believed that whales drink some seawater because the salt is excreted in their urine. Whale urine contains more salt than seawater, and is primarily composed of sodium. 

Ever wondered why whales breach? Find out here

Gray whale

How Do Whales Filter Salt Out of Salt Water?

Whales drink salt water, which means they have a high sodium concentration. This is unhealthy and can lead to severe dehydration and death. Whales have massive kidneys, and their efficiency allows the whale to filter out salt without sacrificing the water their bodies require. 

Whales filter salt water from their bodies. They do this by reabsorbing more water into the kidneys. Whales use their 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. 

How Does A Whale’s 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 salt 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.  

The differences in kidneys 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 to maintain salt balance.

Do Whales Get Thirsty?

Although whales live in an aquatic environment, 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 loses water and they may become dehydrated. 

In these cases, whales 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 such as krill and squid, which contain water, and taking in small amounts of saltwater which they filter through their kidneys.

Do you know which animals drink salt water? Find out here.

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

Nature Journal – Mellanby, K. (1942). Metabolic water and desiccation. Nature150(3792), 21-21