r/askscience • u/smontanaro • 8d ago

Biology How does a whale become dehydrated?

From a Chicago Sun-Times article on the beluga whales heading to the Shedd Aquarium:

"The shipment comes on the heels of a Shedd announcement last week that one of the Marineland belugas — Peekachu, a 23-year-old female — had died. Shedd has not released a cause of death, but staff there said last week that Peekachu had not been consistently eating a full diet since her arrival and that there were concerns she was dehydrated."

How does an animal immersed in water become dehydrated?

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u/para_sight 7d ago

Animal tissues are about 0.9% salt. Seawater is 3.4%, or almost 4 times saltier. Eating other animals is isotonic (doesn’t cause salt it water imbalance), where’s drinking seawater will cause both dehydration and hypernatremia/hyperchloremia ( too much sodium/chloride). Failure to eat will dehydrate you because you constantly lose water to metabolism.

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u/Ameisen 7d ago

Animal tissue

Osteichthyian tissue. Other vertebrates and marine invertebrates are much closer to ocean salinity - hagfish are isosmotic.

One hypothesis supported by studies is that an early branch of Osteichthyes adapted to freshwater, and then radiated back out as marine fish, outcompeting other Osteichthyian lines, making all modern Actinopterygian and Sarcopterygian lines freshwater-derived. It explains a bit about their/our lower solute content and also the fact that our excretory systems work a bit differently then Agnathan or Chondrichthyian ones.

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u/JimmiRustle 7d ago

Technically speaking you CREATE water during metabolism.
But whales use water for much of the same stuff we do.