Reading Comprehension — quick quiz

Read the passage carefully and answer the question that follows. The Indian elephant is smaller than the African elephant. It has smaller ears and a more curved back. Indian elephants are found in the forests of India, Sri Lanka, and other parts of Asia. These gentle giants are herbivores and spend about 16 hours a day eating grass, leaves, and bark. They are highly intelligent animals and can recognize themselves in a mirror. Elephants live in groups called herds, led by the oldest female elephant. They communicate with each other through sounds that humans cannot always hear. What is the main idea of this passage?