People are the only animals that talk in words and sentences. But many animals do give signals to each other. For example, a starling screams when it is frightened. The cry of alarm warns other starlings of danger. A mother cat makes a special kind of meow when she calls her kittens. Horses whinny to greet their companions. Crickets attract their mates with a noise they make by rubbing the sawtoothed edge of one wing across the ridges in the opposite wing. Many birds sing to attract mates.
   Bees have a kind of silent "sign language." A professor in Germany discovered it. He noticed that sometimes a bee would come to the hive and perform an excited little dance. The other bees would pay close attention. Then they would fly off straight to a field full of flowers that the first bee had located. The professor studied the dances. Right turns, left turns, little jumps — all had a meaning. The dancing bee was giving directions to a place where nectar could be gathered from flowers. In the end, the professor understood the sign language so well that he himself could go to the field the bee had discovered!