What Are Threatened and Endangered Species?

When people talk about the status of plant and animal species—the current state they are in, or how well they are doing in the world—they rely mostly on three sources: United States Fish and Wildlife Service, International Union for the Conservation of Nature (IUCN), and Convention on International Trade in Endangered Species (CITES). All three of these organizations conduct field studies and population surveys and gather information about threatened and endangered populations from local sources. By coordinating with many other groups, they determine how many individual of a certain species there are in the world. This is usually an approximation, not an exact number, because it would be hard to be absolutely sure that every single animal was counted. Once the number of the population has been determined, then that species is given a term to describe its status, such as "endangered” or "threatened,” although the different agencies may use different terms.

  U.S. Endangered Species Act

Before a plant or animal species can receive protection under the U.S. Endangered Species Act, it must first be placed on the Federal list of endangered and threatened wildlife and plants. This listing program follows a strict legal process to determine whether to list a species, depending on the degree of threat it faces. The terms “endangered” or “threatened” species are defined in the following way.


EndangeredA species in danger of extinction throughout all or a significant portion of its range, as a result of any of the following: habitat change, reduction or destruction, overhunting or excessive capture, disease or predation, lack of regulation or management, or other natural or man-made factors.

ThreatenedA species that is likely to become endangered in the foreseeable future.


The Fish and Wildlife Service, in the Department of the Interior, and the National Oceanic and Atmosphereic Administration (NOAA) Fisheries, in the Department of Commerce, share responsibility for administration of the Endangered Species Act.  The Fish and Wildlife Service maintains the list of plant and animals native to the United States that are candidates or proposed for possible addition to the Federal list. All of the Service’s actions, from proposals to listings to removals (“delisting”), are announced through the Federal Register.

[note: The species counted include listed pinnipeds (seals, etc.) and anadromous fishes under the sole jurisdiction of the National Marine Fisheries Service that use land or fresh waters within the States and Territories of the United States. Species are not broken up into listing entities as they are in the State List reports. Species not listed in a state are not counted, although these may occur there in a non-protected population.]

To use this interactive map of threatened and endangered species in the U.S. click here.


For a listing of threatened and endangered species, candidates for listing, and related information click here

For a summary of  the Endangered Species Act and how it is administered click here



San Diego Zoo. (2005). Animal bytes; Conservation status. Retrieved February 3, 2005 from http://www.sandiegozoo.org/animalbytes/a-status.html

U.S. Department of Fish & Wildlife Service. (2005). Species information; Threatened and endangered animals and plants. Retrieved February 3, 2005 from http://endangered.fws.gov/wildlife.html