An extirpated species is one that no longer occurs in an area but still lives in other areas. The bison, elk, porcupine and black bear are extirpated from Illinois but live in parts of the United States.

An extinct species is one that no longer survives anywhere in the world. The Carolina parakeet once lived in woodlands throughout eastern North America, including Illinois, but is now extinct.

Why do species become endangered or threatened?

Most plants and animals are able to adapt to their surroundings. These species survive, reproduce in large numbers and are considered to be "common." Endangered and threatened species do not adapt as well to changes and reproduce in lower numbers. The reasons a species become endangered or threatened vary but may include some of the following.

> chemical or other toxic pollutant
> loss of important habitat
> introduction of an exotic species, or species that normally lives in other parts of the world
> lack of laws to restrict the numbers taken by hunting, fishing and trapping; this occurred   historically but modern laws prohibit losses for these reasons
> loss of very specific requirements for food, water or shelter needs on the very edge of their   range (the area where their population lives)

Extinction is a natural process. Historically extinction occurred very slowly. Today, with the increased human population and our demand for natural resources, the extinction process occurs much faster.