Animals become endangered due to growing human population, destruction of their habitats, pollution and the introduction of other exotic species in the same region. Human exploitation of Earth's resources also contributes to the endangerment of animal species.
According to the Endangered Species Act, a species can either be classified as endangered or threatened. An endangered species is one whose members are so few that the entire population suffers a high risk of extinction. A species is said to be threatened if it is likely to become endangered within the foreseeable future. The International Union for Conservation of Nature, keeps track of endangered species around the world.
Loss of habitat is the main reason species become endangered. Habitat is not only where animals live, but also where they find food and raise their babies. Humans destroy animals' habitats when they take up the space for their own use, such as building houses.
When new animals are introduced in an area, they may overpopulate the area, compete for food or carry diseases for which the native animals lack immunity. The native animals may also become prey for the new animals. Examples of pollution that endangers animals are industrial emissions, pesticides and burning fuels, such as coal.