# Whales dehydrated in fresh water? **URL:** \ **Category:** Factual Questions\ **Created:** [June 1, 2020, 7:07pm UTC](https://boards.straightdope.com/t/whales-dehydrated-in-fresh-water/854867 "2020-06-01T19:07:04Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [June 1, 2020, 7:07pm UTC](https://boards.straightdope.com/t/whales-dehydrated-in-fresh-water/854867/1 "2020-06-01T19:07:04Z")
As some of you may have heard a humpback whale has come up the St. Lawrence as far as Montreal. A woman described as a marine biologist was on the radio this morning. She claimed that an extended stay in fresh water would result in various problems, one of which was dehydration. Huh? This seems to make no sense. Can anyone explain how immersion in fresh water could result in dehydration? ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [June 1, 2020, 7:46pm UTC](https://boards.straightdope.com/t/whales-dehydrated-in-fresh-water/854867/2 "2020-06-01T19:46:19Z")
Is it possible you might have misheard her? I know for ocean dolphins too much time in Fresh Water is bad for their skin, but dehydration does sound unlikely. They hydrate through what they eat anyway, not drinking water. ---
**Author:** ![puddleglum](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puddleglum/32/137_2.png) [@puddleglum](https://boards.straightdope.com/u/puddleglum)\ **Post date:** [June 1, 2020, 7:54pm UTC](https://boards.straightdope.com/t/whales-dehydrated-in-fresh-water/854867/3 "2020-06-01T19:54:32Z")
Perhaps she meant being beached or otherwise stuck and getting dehydrated that way. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [June 1, 2020, 8:11pm UTC](https://boards.straightdope.com/t/whales-dehydrated-in-fresh-water/854867/4 "2020-06-01T20:11:04Z")
[This article discusses a whale that died in the River Thame](https://www.newscientist.com/article/dn8632-tests-reveal-severe-dehydration-of-thames-whale/)s. Dehydration is cited, and supposed to be from a lack of food which is how the whale would hydrate itself. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [June 2, 2020, 1:30am UTC](https://boards.straightdope.com/t/whales-dehydrated-in-fresh-water/854867/5 "2020-06-02T01:30:58Z")
That article explains that the lack of food apparently caused dehydration since they get water from their foods. Seems that lack of food is the real cause. It’s not so much that she is wrong, but what she said is misleading. If I hear any more about the whale I will update this thread. ---
**Author:** ![pool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pool/32/4152_2.png) [@pool](https://boards.straightdope.com/u/pool)\ **Post date:** [June 2, 2020, 2:06am UTC](https://boards.straightdope.com/t/whales-dehydrated-in-fresh-water/854867/6 "2020-06-02T02:06:56Z")
Why couldn’t a whale get hydration from drinking fresh water, even if there is no food in it? ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [June 2, 2020, 2:37am UTC](https://boards.straightdope.com/t/whales-dehydrated-in-fresh-water/854867/7 "2020-06-02T02:37:50Z")
> [@pool](#): > > Why couldn’t a whale get hydration from drinking fresh water, even if there is no food in it? It may never occur to a whale to do that. A whale that drinks water when dehydrated under normal conditions would become more dehydrated trying to get rid of all that salt from sea water. ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [June 2, 2020, 7:09am UTC](https://boards.straightdope.com/t/whales-dehydrated-in-fresh-water/854867/8 "2020-06-02T07:09:23Z")
Might osmosis play a role? Whales are “calibrated” to live with a certain osmotic pressure from seawater, if the pressure changes due to lack of salt it may destabilize their equilibrium. Just an idea, pure especulation. Do not know if the effect would be anything more than skin-deep (blubber-deep?). ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [June 2, 2020, 7:14am UTC](https://boards.straightdope.com/t/whales-dehydrated-in-fresh-water/854867/9 "2020-06-02T07:14:19Z")
Food should not be the reason, many whale species go for months without food when they migrate from the poles to the warmer waters where they calf, they even breats feed for months without eating while swimming back to the poles. They can metabolize their fat reserves into energy generating water in the process. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [June 2, 2020, 10:46am UTC](https://boards.straightdope.com/t/whales-dehydrated-in-fresh-water/854867/10 "2020-06-02T10:46:48Z")
> [@Pardel-Lux](#): > > Might osmosis play a role? Whales are “calibrated” to live with a certain osmotic pressure from seawater, if the pressure changes due to lack of salt it may destabilize their equilibrium. Just an idea, pure especulation. Do not know if the effect would be anything more than skin-deep (blubber-deep?). IIRC It would be the opposite for ‘fish’, a fresh water fish put in salt water would dehydrate much like a person drinking sea water. For the other way around it would/may overhydrate whatever that term is as more water would enter then it can handle. Some fish can handle this transition however. Since this is for fish IDK how whales fit into this.