The southwestern red squirrel or Fremont's squirrel (''Tamiasciurus fremonti'') is a species of

tree squirrel Tree squirrels are the members of the squirrel family (Sciuridae) commonly just referred to as "squirrels." They include more than 100 arboreal species native to all continents except Antarctica and Oceania. They do not form a single natural, or ...

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to high-altitude regions of the

southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, ...

Taxonomy

It was formerly considered conspecific with the

American red squirrel The American red squirrel (''Tamiasciurus hudsonicus'') is one of three species of tree squirrels currently classified in the genus '' Tamiasciurus'', known as the pine squirrels (the others are the Douglas squirrel, ''T. douglasii'', and the s ...

(''T. hudsonicus''), but a 2016 study found sufficient phylogenetic evidence indicating it was a distinct species. The

American Society of Mammalogists The American Society of Mammalogists (ASM) was founded in 1919. Its primary purpose is to encourage the study of mammals, and professions studying them. There are over 4,500 members of this society, and they are primarily professional scientists w ...

accepted the results of this study. The

Mount Graham red squirrel The Mount Graham red squirrel (''Tamiasciurus fremonti grahamensis'') is an endangered subspecies of the southwestern red squirrel (''Tamiasciurus fremonti'') native to the Pinaleño Mountains of Arizona. It is smaller than most other subspeci ...

(''T. f. grahamensis'') is a notable, endangered subspecies of the southwestern red squirrel. In addition, genetic sampling indicates that squirrels from the Sacramento Mountains of New Mexico form a highly divergent clade that dates back to the

Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eur ...

, about 130,000 years ago. Squirrels in the San Mateo Mountains also appear to be genetically divergent, although this is only based on a single individual.

Distribution

It ranges from the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...

of southern

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the ...

into the

Sacramento Mountains The Sacramento Mountains are a mountain range in the south-central part of the U.S. state of New Mexico, lying just east of Alamogordo in Otero County (small portions of the range lie in Lincoln County and Chaves County). From north to south, ...

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe, New Mexico, Santa Fe , LargestCity = Albuquerque, New Mexico, Albuquerque , LargestMetro = Albuquerque metropolitan area, Tiguex , Offi ...

and the

Mogollon Mountains The Mogollon Mountains or Mogollon Range ( or ) are a mountain range in Grant County and Catron County of southwestern New Mexico, in the Southwestern United States. They are primarily protected within the Gila National Forest. Geography The Mo ...

in both New Mexico and Arizona. Its range overlaps with that of ''T. hudsonicus'' in the southern Rocky Mountains.

Habitat

They largely inhabit mixed coniferous and

spruce-fir forests A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal ( taiga) regions of the Earth. ''Picea'' is the sole genus in the subfa ...

. Although they occasionally venture down into

ponderosa pine ''Pinus ponderosa'', commonly known as the ponderosa pine, bull pine, blackjack pine, western yellow-pine, or filipinus pine is a very large Pinus, pine tree species of variable habitat native plant, native to mountainous regions of western Nor ...

forests, they are absent from ranges that do not include the higher-elevation spruce-fir and mixed coniferous forests. Due to the limited range of this habitat, the population of southwestern red squirrels is naturally fragmented and has little gene flow between subpopulations; these populations may have been more widespread during the last glaciation, when these forests were more connected. Fossil remains of this species are known from the

Guadalupe Mountains The Guadalupe Mountains ( es, Sierra de Guadalupe) are a mountain range located in West Texas and southeastern New Mexico. The range includes the highest summit in Texas, Guadalupe Peak, , and the "signature peak" of West Texas, El Capitan, both ...

, indicating that they likely once had a suitable climate.

Conservation

There is little evidence of demographic-driven expansion in populations of this species, and mountain ranges each have their own highly-divergent clades of species, indicating high separation and little gene flow between populations. If this lack of connectivity is compounded with further

degradation Degradation may refer to: Science * Degradation (geology), lowering of a fluvial surface by erosion * Degradation (telecommunications), of an electronic signal * Biodegradation of organic substances by living organisms * Environmental degradation ...

of their habitats, the population dynamics of this species could eventually be driven by

extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

. Thus, this species is thought to be of high conservation concern. One notable subspecies, the

, is already thought to be endangered.

References

{{Taxonbar, from=Q89875686 Tamiasciurus Squirrel, Southwestern Red Squirrel, Southwestern Red Endemic fauna of the Southwestern United States Fauna of the Rocky Mountains Natural history of Arizona Taxa named by John James Audubon Taxa named by John Bachman Mammals described in 1853