Vicuñas live high in the Andes mountains of South America yet are never short of breath. At about 4,000 m (13,000 ft) above sea level humans would suffer breathlessness, but vicuñas can sprint effortlessly up rocky slopes, and on level ground they can run at nearly 50 km/h (30 mph).
These graceful cinnamon-coloured relatives of camels have normal mammalian lungs, but they have about three times as many red blood cells a litre of blood as humans. Their red cells last twice as long and because these cells contain an unusual form of
the red blood pigment haemoglobin, they are better at collecting oxygen. Altogether, it adds up to an ideal high- altitude breathing system.
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