About 490 species of mammals are recorded in the United States. Unincorporated territories such as Puerto Rico, Guam or Northern Mariana Islands are not covered. Mammals introduced and extinct in the Holocene except Pleistocene/Holocene boundary are included.
According to the IUCN Red List 3 of these species are critically endangered, 20 endangered, 15 vulnerable, 20 near threatened and 4 extinct.[1]
Some species are identified as indicated below:
The following tags are used to highlight each species' conservation status as assessed by the International Union for Conservation of Nature:
| EX | Extinct | No reasonable doubt that the last individual has died. |
| EW | Extinct in the wild | Known only to survive in captivity or as a naturalized population well outside its previous range. |
| CR | Critically endangered | The species is in imminent risk of extinction in the wild. |
| EN | Endangered | The species is facing an extremely high risk of extinction in the wild. |
| VU | Vulnerable | The species is facing a high risk of extinction in the wild. |
| NT | Near threatened | The species does not meet any of the criteria that would categorize it as risking extinction but it is likely to do so in the future. |
| LC | Least concern | There are no current identifiable risks to the species. |
| DD | Data deficient | There is inadequate information to make an assessment of the risks to this species. |
(v. 2013.2, the data is current as of March 5, 2014[1])
and the Endangered Species Act:
| E | Endangered |
| T | Threatened |
| XN, XE | eXperimental Nonessential or Essential population |
| E(S/A), T(S/A) | Endangered or Threatened due to Similarity of Appearance |
(the data is current as of March 28, 2014[2])