Can animals be made to work for us?（二）
Of course,as we know,dogs can be used to guard a house,and soldiers in both old and modern times have used geese to give warning by making a lot of noise when a stranger or an enemy comes near.But it may be possible to train animals to work in factories,In Russia,for example,pigeons,which are birdswith good eyesight,are being used to watch out for faults in small steel balls that are being made in one factory.When the pigeon sees a ball which looks different from others,it touches a steel plate with its beak （鳥嘴）.This turns on a light to warn people in the factory.At the same time a few seeds are given as a reward.It takes three to five weeks to train a pigeon to do this and one pigeon can inspect 3,000 to 4,000 balls an hour.
Apes （類人猿） have been used in American in helping to make cars,and scientists believe that these large monkeys maybe one day gather crops and even drive trains.