Question: Which species of animal has the most efficient kidneys?

Keith Siew answered on 26 Jun 2013:

Probably the Kangaroo mouse!

It lives in an arid climate… basically desert and very little if any available drinking water! The animal is nocturnal and it’s kidneys are so efficient it practically never needs to drink water (it gets what it needs from food instead).

The reason why it’s kidneys are so effect is to do with the length of its loop of henle… this is a part of the nephron (the small functional units of the kidney with about 0.8 – 1.2 million per kidney)… here salt is reabsorbed and deposited deep in the kidney. Along the length of the loop the fluid gets increasingly more concentrated with salt and this fluid surrounds the tubes which contain the filtered fluid which will eventually become urine. So if you remember the process of osmosis… water wants to move from a place of low solute (in this case salt) concentration to a place of higher concentration… so the high salt concentration in the kidney’s fluids surrounding these tubes effectively draws the water out of the urine and reabsorbs it… so you lose very little water and produce very concentrated urine!

The Kangaroo mouse actually helped us work out some of the functions of our own kidneys! Incredible little creatures!