Not many animals choose to move around on two legs. The life of a four-legged animal is much easier on the spine and on the skeleton as a whole.
Most birds have better things to do with their forelimbs, such as flying! The ostrich, however, has never been granted the gift of flight. Despite this, the ostrich has maintained the two-legged lifestyle of its feathered cousins.
When you are travelling at such high speeds it is important to be able to see where you are going and the ostrich is well equipped in this department. Their eyes are the largest of any land animal, and, at 5 centimetres in diameter, they are bigger than their brains!
The Kalahari is a harsh environment for ostriches, however, as far as predators are concerned. Lions, leopards, cheetahs and hyaenas all stalk the night. The ostrich is never perfectly at rest, having always to keep an eye out for any of the predators that would happily make a meal out of them.