Not So Supernatural: How Do Marine Mammals Hydrate?

I didn’t know yesterday was World Oceans Day, but luckily I did spend some time in the ocean. This summer, I have a weekly surf club going on. No, this is not a picture of me, but it could be. I’ll tell you a secret: I’m totally afraid of the ocean. Yes, me, who spent whole summers at the beach growing up. Me, a born island girl. Me, who loves no place more than the coast. Why? Because it’s an abyss out there. I honestly get thrashed every time I paddle out, but I keep trying, and that’s cool.

This is beside the point, though. The thing is, I’ve swallowed my fair share of sea water. It sucks, and it wipes me out and makes me super thirsty.

So, my burning question this week is: How do marine mammals hydrate?

Scientists believe that marine mammals such as dolphins, whales, and seals get most of their hydration from consuming their prey. As they digest prey such as fish and krill, they extract water through the metabolic process of carbohydrates and fats (water is a by-product of metabolism). They don’t need to hydrate as much as humans do since their bodies don’t lose nearly as much water as ours (we sweat, they don’t). As for swallowing sea water, it’s believed that they don’t do it intentionally, only incidentally while ingesting prey. Saltwater doesn’t dehydrate them the same way it would a terrestrial mammal, though. Marine mammals have more sophisticated kidneys, which are more efficient at processing salt and excreting it through urine.

(Sources: Whale and Dolphin Conservation, Scientific American, The Journal of Experimental Biology)

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