Marine species have developed unusual adaptations for filtering salt from the water they require.
Q. Humans can’t drink seawater. So what do sea lions, whales, dolphins and sea birds drink?
A. Marine animals may consume both freshwater and saltwater. They rely on various adaptations for survival when only saltwater is available.
Many marine mammals have specialized organs called reniculate kidneys with multiple lobes, increasing their urine-concentrating efficiency beyond that of humans. These animals can handle high concentrations of salt in seawater without becoming dehydrated by salt buildup, as humans would.
Experts now believe, however, that many of these creatures drink seawater only occasionally. Instead they get low-salt water from what they eat or manage to produce it on their own.
Whales, for example, have the specialized kidneys but need far less water than land mammals. Whales get water mostly from the small sea creatures, like krill, that form much of their diet.
A version of this article appears in print on
, on Page
of the New York edition
with the headline:
Freshwater Is Optional for Some Animals. Order Reprints | Today’s Paper | Subscribe