Dolphins in salt water

From: Jennifer Philips (
Date: Mon May 07 2001 - 00:13:09 EDT

Hi my name is Samantha and I am 9 years old. My dad and I are trying to
out why dolphins live in salt water and not fresh water. Can you help us.




Good question! Dolphin's have lived in the oceans for something like 50
millions years. Coming from land-dwelling mammals, they had to go through a
lot of adaptations to make survival in the salty oceans possible. Their
kidney's are much larger to better remove excess salt from the blood, and
their skin is adapted to control the transfer of salt into the body. They
also are able to get all of the fresh water they need from the bodies of the
fish they eat. Marine dolphins can live for a short time in fresh water, but
soon their bodies begin to fail them! In fresh water, their kidney's and
skin still try to function as if they are having to control salt levels.
Soon, they become diseased, and would not survive if they did not return to
the ocean.

Thank you for your question,
Jen Philips

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