{"id":2155,"date":"2026-03-18T14:42:56","date_gmt":"2026-03-18T14:42:56","guid":{"rendered":"https:\/\/owspakistan.com\/?p=2155"},"modified":"2026-03-18T14:42:56","modified_gmt":"2026-03-18T14:42:56","slug":"how-do-sea-mammals-stay-hydrated","status":"publish","type":"post","link":"https:\/\/owspakistan.com\/?p=2155","title":{"rendered":"How marine mammals stay hydrated in a salty sea"},"content":{"rendered":"
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Over the long and complicated course of evolutionary history, mammals independently turned towards water to make a home multiple times. While many of the warm-blooded animals that abandoned dry land for a watery habitat no longer exist, we still have plenty of stunning examples: Think dolphins, whales, manatees, porpoises. There\u2019s even a whole suborder of carnivores called the pinnipeds, which includes seals, sea lions, and walruses who move between land and water.\u00a0<\/p>\n

But, just like all animals, marine mammals need water to stay hydrated to survive. The trouble is that salt water, which makes up some 97 percent of the water on earth and is home to mammals like orcas and bottlenose dolphins, is dehydrating by nature. \u201cWe have salt in our body fluids, but a lot less salt than in sea water,\u201d Martin Grosell<\/a>, an aquatic organisms researcher at the University of Miami, tells Popular Science<\/em>. \u201cThis means that the high salt concentration in sea water, by osmosis, drags water out of the animal.\u201d\u00a0<\/p>\n

Despite the fact that you get wet when you enter the ocean, living in the sea is physiologically similar to living in a desert, Grosell adds. To live in any tough scenario, on land or otherwise, animals must adapt. To understand how mammals can survive and hydrate in the sea, we must dive in the evolutionary deep end.\u00a0<\/p>\n

The difference between invertebrates and vertebrates<\/h2>\n

While scientists still can\u2019t pinpoint the exact origin of life, many scientists believe it actually started deep in the ocean<\/a>. But these early creatures hardly resemble what we think of as today\u2019s sea beasts\u2014they were invertebrates, meaning they didn\u2019t have backbones.\u00a0<\/p>\n

\u201cMost of the invertebrates do not control their internal salt content, so they have the same salt content as the sea water,\u201d says Grosell. \u201cWhat that means is they are not dehydrating, they\u2019re not losing water.\u201d This strategy for survival, called osmoconforming, appears in all sorts of animals we are familiar with today: starfish<\/a>, jellyfish<\/a>, lobsters<\/a>, mollusks<\/a>, and more.\u00a0<\/p>\n

But things get complicated when you throw in a backbone. Fish<\/a>, sea reptiles (think sea snakes and saltwater crocodiles<\/a>), sea mammals, and even sea birds<\/a> all require specialized body parts to remove the salt from the water they consume.\u00a0<\/p>\n

\u201cThe big challenge for animals that drink sea water is the salt they\u2019re getting with that water, \u201d Grosell says. \u201cIf they cannot get rid of that salt, there\u2019s no benefit to taking in that water.\u201d\u00a0<\/p>\n

For fish, drinking salt water is just part of the day-to-day. The water gets absorbed into their intestines, but the salt is transported from their blood to cells in the gills, which then push that salt back into the sea.\u00a0<\/p>\n

\"An
Humpback whales have really salty pee, relying on specialized kidneys to filter out salt from ocean water. Image: Getty Images \/ <\/em> Westend61<\/figcaption><\/figure>\n

But for animals without gills, like mammals, reptiles, and birds, the story is more complex. These creatures need to expel the extra salt somehow, which for mammals is via the kidneys. While it\u2019s exceptionally difficult to measure, say, the saltiness of whale urine, what we do know is that the kidneys of marine mammals can \u201cproduce a urine that\u2019s really concentrated,\u201d Grosell adds. Some marine animals even have what are called reniculate kidneys<\/a>. These organs are divided into hundreds of tiny filtering units that help expel a ton <\/em>of salt.\u00a0<\/p>\n

Birds, on the other hand, have glands above their eyes that secrete high-salinity fluid like a mammal\u2019s kidney would. This comes in handy for feathered friends who spend swaths of the year with only access to saltwater, and research has demonstrated that salt gland masses of different birds may even vary seasonally<\/a>.\u00a0<\/p>\n

For reptiles, the process is quite similar. Sea turtles have salt glands behind their eyes (which makes them look like they are crying when above the water), marine iguanas have salt glands connected to their nose (which makes for some very salty sneezes), and sea snakes and crocodiles have salt glands on their tongues.<\/p>\n

To drink or not to drink<\/h2>\n

While some animals certainly do, purposefully or otherwise, drink salt water and then deal with the consequences, this is a very metabolically expensive way to live. \u201cIf they can get water in other ways, they\u2019re gonna prefer that,\u201d Grosell adds. \u201cAnd some of those ways, of course, are the water that\u2019s contained in whatever prey they eat.\u201d\u00a0<\/p>\n

Almost all marine mammals are carnivores: Think orcas<\/a>, whales<\/a>, dolphins<\/a>, and even walruses<\/a> and otters<\/a>. Even baleen whales eat swarms of tiny animals known as krill. Chowing down on fish and other marine creatures means eating animals with a similar water content as themselves, and it turns out to be a solid hydration strategy.\u00a0<\/p>\n

For instance, one study from the 1970s demonstrated that this kind of lifestyle, merely chowing down on fish, allows for enough hydration that elephant seal pups don\u2019t even need a sip of fresh water<\/a> to stay healthy. In fact, they can fast on land for up to three months without drinking thanks to their unique combination of behavioral and physiological water conservation mechanisms.\u00a0<\/p>\n

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Still, some marine mammals can\u2019t resist a mouthful of unsalted goodness. This is especially true of manatees, which will seek fresh water sources near the shore or low-salinity river mouths, adds Grosell.\u00a0<\/p>\n

Floridians may attest to this, he says, as manatees<\/a> will sometimes approach boaters for a tasty sip. \u201cThey have a very strong ability to find water,\u201d he says. \u201cWater is a commodity for them, and it\u2019s one they will work hard for.\u201d\u00a0<\/p>\n

On the other side of North America, hooded seal pups found off the Davis Strait, the coasts of Labrador and Newfoundland, and the Gulf of St Lawrence have been recorded slurping up sea water as well as snow<\/a>. Snow, even when it falls over the ocean, is freshwater thanks to the tricks of evaporation.\u00a0<\/p>\n

The key to remaining a hydrated mammal while thriving in sea water is threefold: eat watery food, find freshwater as needed, and pee out any extra salt that gets in the way. It\u2019s a tried-and-true method that\u2019s lasted millions of years. But humans don\u2019t have these adaptations. So next time you hit the beach<\/a>, remember to pack a water bottle if you don\u2019t want to dehydrate<\/a>.<\/p>\n

In <\/em>Ask Us Anything<\/em><\/a>, Popular Science answers your most outlandish, mind-burning questions, from the everyday things you\u2019ve always wondered to the bizarre things you never thought to ask. Have something you\u2019ve always wanted to know? <\/em>Ask us<\/em><\/a>.<\/em><\/p>\n

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