46.They sometimes travel more than sixty miles to find food or water, and are very good at working out where other elephants are-even when they are out of sight. 

47.The researchers are convinced that the elephants always know precisely where they are in relation to all the resources they need,and can therefore take shortcuts, as well as following familiar routes.

48.One possibility was that they merely used their eyes and tried out the plants they found, but that would probably result in a lot of wasted time and energy, not least because their eyesight is actually not very good.

49.The volatile chemicals produced by plants can be carried a long way, and they are very characteristic: Each plant or tree has its own particular odor signature. 

50.The experiment showed that elephants may well use smell to identify patches of trees that are good to eat. And secondly to assess the quality of the trees within each patch. Free-ranging elephants presumably also use this information to locate their preferred food.