Sciurus (and Tamiasciurus) are thoroughly at home in trees and spend most of their time in them. With most of the region now in grassland or shrubland, habitat for tree squirrels is limited to riparian growth along river valleys and montane forests. Several members of the genus currently occur in our region.
Sciurus aberti occurs predominantly in Ponderosa Pine forest, though it may venture into mixed coniferous forest at times. Historically, it occurred in the western and northern mountains of New Mexico. There is conflicting data regarding the mountains east of the Rio Grande and south of the Sangre de Cristo Mountains (Findley et al. 1975). They may or may not be native to the Sandia Mountains. They appear to have colonized the Manzano Mountains to the south from the Sandias sometime during the middle of the 20th century. They are unknown from farther southeast of the Rio Grande. The restricted distribution in New Mexico of Ponderosa Pine forest until some time around the end of the Pleistocene may explain the lack of occurrence in the east. The macrofossil evidence for Ponderosa Pine is limited to one site in the San Andres Mountains, with the species absent from glacial-age sites north of about 33.5° N latitude (Norris et al. 2006). Quite likely, the lowlands south of the Sangre de Cristos were deforested before the squirrel spread into the area from the west and north.
Sciurus arizonensis occurs in riparian habitat in mountain valleys in the western portion of Catron County, NM (Findley 1987) and adjacent Arizona. Slaughter (1975) recorded Sciurus cf. S. arizonensis from Blackwater Draw Loc. No. 1 on the basis of a P4 that "resembles the Arizona Gray Squirrel more closely than the other two possibilities, Abert's Squirrel and the Fox Squirrel . . . ." (p. 182). Harris (1977) suggested that S. carolinensis would make more sense than S. arizonensis, which is limited to the Pacific drainage. He suggested that the record could pertain to a population of the Eastern Gray Squirrel moving up riparian growth along Blackwater Draw. However, S. carolinensis occurs today no closer than in approximately the eastern fourth of Texas, whereas the Fox Squirrel closely approaches the eastern border of New Mexico. I've opted for leaving this record as Sciurus sp.
The identity of the Lower Sloth Cave (Logan 1983) squirrel is up in the air. The environment at the time of deposition would make S. aberti seem most likely, but if the geographic and local temporal range of S. aberti was as indicated above, that species should not have been there. Neither of the other two species mentioned above would seem likely to have been in the high-elevation coniferous forest zone as indicated by the woodrat midden record in the nearby and approximately contemporaneous Upper Sloth Cave (Van Devender et al. 1977).
A fourth species of Sciurus, S. nayaritensis (Apache Fox Squirrel), occurs in our region, but almost entirely in Mexico. It is a primarily Mexican species that has a presence in the Chiricahua Mountains of southeastern Arizona.
Literature. Findley 1987; Findley et al. 1975; Harris 1977; Norris et al. 2006; Logan 1983; Slaughter 1975; Van Devender et al. 1977.
Tree squirrel teeth are quite distinctive from those of ground squirrels, but isolated teeth are difficult to assign to species.
Wisconsin: Carpinteria (Wilson 1933).
Mid/Late Wisconsin: Sandblast Cave (Emslie 1988).
Late Wisconsin: Blackwater Draw Fauna (Slaughter 1975); Lower Sloth Cave (Logan 1983).
Literature. Emslie 1988; Logan 1983; Slaughter 1975; Wilson 1933.
Fig. 1. Abert's Squirrel. Photograph by Sally King, courtesy of the US National Park Service.
Medial Irvingtonian: SAM Cave (Rogers et al. 2000).
Mid Wisconsin: Papago Springs Cave (Czaplewski and Mead et al. 1999: cf. gen. et sp.).
Literature. Czaplewski and Mead et al. 1999; Rogers et al. 2000.
Last Update: 28 Dec 2013