What do pandas，tigers，whales，lions and wild camels have in common （共同的）？They are all endangered（濒临灭绝的）. Here are the reasons.
Hunting：For centuries，people hunted elephants for their tusks，killed tigers for their fur，and caught many other animals for their meat.
Foreign animals：In 1505，some people discovered a beautiful island named Mauritius in the Indian Ocean. People brought dogs，pigs，monkeys and rats with them，but this was bad news for dodo birds. The birds did not have natural enemies （天敌） before. They ate fruit that fell from trees and built their house on the ground. But when people came，dodo birds were in big trouble—men killed them for their meat，and the new animals broke their homes and ate their eggs. The number of dodo birds became smaller and smaller and finally extinct. The last dodo bird was killed in 1681.
Loss of living space：People cut down forests for farming and building houses. People build dams （水坝） to make sure they have enough water. While we make our lives comfortable，other animals have less and less space.
