Why are the male elephants sent away?

The elephant is the biggest four-legged animal in the world. They live for a long time—fifty or sixty years in families of females. There will be a few young male—a few "baby boy". But the females will soon send them away. An elephant family keeps only its daughters, mothers and grandmothers, and its great grandmothers.
    The females stay together for years. The older animals look after the young ones. The mothers teach their daughters and set a good example.
    And what happens to male elephants? Well, the young males stay with their mothers for a time. Then they must leave the family. The females just send them away. A bull elephant does not often have a friend. He lives alone; away from the family, and often away from other bulls.
    Sometime the females call a bull. He can visit them then, and they stay for a time. But soon his "wives" and sisters send him away again. The females have a very happy family life.
    Elephants can remember things very well. They never forget great happiness or great sadness. When a female elephant dies, her daughters and her grand-daughters are sad for many months. They stay with the dead body. Then they carry a bit of it away with them. They never forget a dead friend.