In the past 300 years, more than 130 kinds of animals have becomeextinct. One of these extinct kinds is the passenger pigeon (旅鸽). At one time there were millions of these birds in North America, but now there are none. The last one died in the Cincinnati Zoo in 1914. Another extinct animal is the cape lion (西非狮). The animal has been extinct since 1860. What causes animals to become extinct? Too much hunting is one cause; pollution is another. Governments around the world have begun to protect wild animals in danger. In the United States, the US Fish and Wildlife Service is responsible for (承担义务) endangered animals. It has listed nearly 200 kinds of endangered animals in North America.