How many different species of animals live in the USA?

The exact number of different animal species living in the United States is not precisely known, as new species are discovered and more research is conducted. However, the following are some estimates of the number of animal species in the United States:

- According to the Integrated Taxonomic Information System (ITIS), a partnership between the United States and Mexico that provides scientifically credible taxonomic information on plants, animals, fungi, and microbes, there are around 88,297 species of animals in the United States.

- According to the National Wildlife Federation, there are roughly 3,933 native terrestrial species and several tens of thousands of aquatic species in the United States, excluding microorganisms and many invertebrate groups.

- The U.S. Fish and Wildlife Service, an agency of the Department of the Interior, recognizes and protects over 2,298 native freshwater fishes, birds, mammals, insects, plants, crustaceans, corals, arachnids, mollusks, echinoderms, annelids, flatworms, cnidarians, sponges, fungi, lichens, algae, mosses, liverworts, ferns, conifers, flowering plants, club mosses, horsetails, whisk ferns, and protozoans in the United States and its territories.

It's essential to note that ongoing taxonomic revisions and discoveries may change these estimates over time. Also, these lists don't factor in non-indigenous species as a result of introductions into specific habitats.