Whales are incredibly well-adapted to living in the sea. Their streamlined bodies are propelled forward by their fluke and flippers, and they breathe through a blowhole on the top of their heads.
They are even able to breastfeed their babies underwater, which is no mean feat. But given that whales have no access to fresh water, how has evolution solved the problem of what they drink?
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Humans cannot drink seawater because the high salt content would lead to dehydration. Whales are much more capable of dealing with seawater than we are due to their specialised kidneys, but they do not drink it very often.
When they do drink seawater, it tends to be accidental – they might be swallowing krill or fish and inadvertently gulp down a few litres.
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Whales get their water from their diet instead; both from ‘free water’ within their prey’s body, and through ‘metabolic water’, where water is produced from the breakdown of their prey.
While whales do need fresh water, they actually don’t need a huge amount, considering their size. This is largely because, in contrast to humans, whales don’t lose a significant amount of water through their skin.
