Whales drinking water?

From: Erich Hoyt (EHoyt@compuserve.com)
Date: Wed Feb 06 2002 - 06:28:02 EST


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Message text written by Zachary Beane

"
Howdy. I got your email address from
http://whale.wheelock.edu/whalenet-stuff/ASK_SCI.html, after searching
Google for "whale expert." I hope you don't mind this message.

Some friends and I were talking about whales and the subject of
drinking came up. People (and I assume other land mammals) have to
drink water pretty frequently or they will dehydrate and die. How do
marine mammals take in water? Is it absorbed through the skin somehow?
Is it ingested and absorbed some other way? Are they "drinking" all
the time, or does it only happen part of the time? How do they deal
with the salt content of the water?

Thanks in advance,
Zach

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Dear Zach,

Marine mammals such as whales live surrounded by salt water and some
swallow certain amounts when they eat, yet they are able to maintain body
fluid equilibrium of salt concentration similar to that of land mammals.
Some researchers say that marine mammals are similar to desert mammals in
their ability to survive with reduced fresh water sources.

Marine mammals can take in fresh water from their food such as fish. Seals
and sea lions have been shown to be able to maintain water balance solely
by the food intake of fish, without access to fresh water. Something called
antidiuretic hormone appears to be involved in the regulation of urine
volume in dolphins. Some marine mammals can produce urine concentrated
enough to indicate their ability to tolerate modest or regular drinking of
sea water but the mechanisms for doing this are not known.

I hope this answers your questions? There is a much fuller explanation
about "living in water: Solutions to physiological problems" on pp. 103-105
(sections on water and salt balance, and on seawater drinking) in Biology
of Marine Mammals, edited by John E. Reynolds III and Sentiel A. Rommel,
1999, Smithsonian Institution Press.

Sincerely,

Erich Hoyt



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