Science Questions

Whales are mammals, but they only consume salt water. This would be dangerous for land mammals, so do sea mammals filter out the salt? Alan, Orpington

Not all sea mammals, such as whales, dolphins, seals and walruses, actually drink sea water, which begs the question where do they get their water?  We think these mammals get their non-salty water from the food that they eat, and they are able to extract that from the fish that they consume.  There are also other adaptations in their kidneys.  We can’t drink seawater because our kidneys cannot cope with that much salt.  Whales and dolphins have special kidneys, which can cope with such large salt concentrations.

April 2007