Cool things you didn't know - 2 - Water of metabolism: Some animals never drink.

Kangaroo rat (added in post) in the Palm Springs Desert


Water is necessary for life.  And yet, there are plants and animals that don't need direct access to it in order to thrive.  A good example of that is the kangaroo rat, a rodent that is neither a rat nor a mouse.  They live in arid regions of North America.  Although they are capable of drinking water, an individual may go its entire life without ever drinking.  That's because they get their water from somewhere you may not expect.

As you probably know, photosynthesis involves turning sunlight into sugar by using carbon dioxide and water.  The opposite of this is cellular respiration, the cellular process of converting sugar (and other foodstuffs) into carbon dioxide and water.  The carbon dioxide is dealt with through breathing (CO2 out and O2 in).  The water stays behind.

The ability of kangaroo rats to conserve water is amazing.  The seeds eaten by kangaroo rats may contain some water internally, but most of the water is produced through cellular respiration.  One gram of seed can produce about half a gram of water.  

Many animals rely on kidneys to remove metabolic wastes, but they use a large amount of water to do so.  For example, human urine contains about 95% water.  Kangaroo rats produce extremely concentrated urine to the point that it is usually excreted in a crystalline form.  

They don't sweat.  They are nocturnal to reduce extreme heat.  They plug up their burrows to keep humidity high.  And they have a counter-current moisture exchange system in their noses that increases the humidity of air coming into the system while decreasing the humidity of the air leaving it. 

The kangaroo rat is perhaps the most water-efficient mammal on the planet.  Whoever could imagine that such a small animal would have such great power.  Maybe it should be a Pokémon?

Thanks for reading.

Eric Svendsen     www.ericspix.com

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