The building of a highway might cut across the territory of a wide ranging herd of elk or a panther. Pollution is a serious threat to wild life, especially in areas where lots of people live. Carelessly thrown away garbage, sewage, and chemical containers contaminate the soil, rivers, and sea. Gases from factories and cars pollute the air. Too much pollution can ruin an animal's habitat.
Animals also die directly at the hands of people through hunting and fishing.
Wild animals are killed for food, for sport, and for their fur, skin, horns, or shells. Too many hunters chasing one particular kind of animal may wipe it out entirely. Parrots, frogs, tortoises, and other foreign animals make popular pets. Although some are bred in captivity for the pet market, some are still captured in the wild. Not all countries have as stringent import regulations as those now enforced in the United States.