Every candidate species is assigned a priority number from 1 to 12 based on factors such as the magnitude of threats facing the species, the immediacy of the threat and the species' taxonomic status. A lower priority number means that the species is under greater threat. For example, a number of 2 indicates a higher degree of concern than a number of 8.[3]
The following table shows how the FWS determines listing priority numbers.[4]
Threat Magnitude
Immediacy
Taxonomy
Priority Number
High
imminent
monotypic genus
1
species
2
subspecies/population
3
non-imminent
monotypic genus
4
species
5
subspecies/population
6
Moderate to low
imminent
monotypic genus
7
species
8
subspecies/population
9
non-imminent
monotypic genus
10
species
11
subspecies/population
12
References
^Randall, Jan A. (2018). Endangered species: a reference handbook. Contemporary world issues. Santa Barbara, California: ABC-CLIO, an imprint of ABC-CLIO, LLC. ISBN978-1-4408-4899-5.
^Shogren, Jason F.; Tschirhart, John, eds. (2001). Protecting endangered species in the United States: biological needs, political realities, economic choices. Cambridge ; New York, NY: Cambridge University Press. ISBN978-0-521-66210-9.