This is a question that has always bothered me. A quick internet search yields "metabolic processes" as the reason for how marine mammals obtain water, but what are those processes and why don't land mammals have them? In other words, what are the specific differences between marine and non-marine mammals in how they stay hydrated?

  • $\begingroup$ @Charles correct me if I'm wrong, but isn't marine biology (and the word marine) referring directly to the ocean and therefore salt water? $\endgroup$
    – BlackThorn
    Aug 22, 2017 at 16:45
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    $\begingroup$ Upon searching google, there are dozens of results that directly answer this. For example, here. However, it seems that you're asking two separate questions in your post, those being: 1) "How do marine mammals stay hydrated?" and, 2) "Why don't land mammals have those [metabolic processes] too?". I would suggest focusing on just one. $\endgroup$
    – user22020
    Aug 22, 2017 at 16:57
  • $\begingroup$ "For most whales and dolphins, however, we simply do not know how they get their water, because it is difficult to observe these animals." That is a troubling line :( The article seemed to conclude that some marine mammals have more efficient kidneys? $\endgroup$
    – BlackThorn
    Aug 22, 2017 at 16:58
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    $\begingroup$ "... marine mammals that feed on fish consume food with a salt content similar to that of their own blood, thereby avoiding the problem entirely. Indeed, a study of California sea lions showed that, on a diet of fish, these animals can live without drinking fresh water at all. Some species of seals and sea lions apparently do drink seawater at least occasionally, as do common dolphins and sea otters, but the practice is very rare in some other species." $\endgroup$
    – user22020
    Aug 22, 2017 at 17:05


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