Key to the ground squirrels of Arizona

This key to the ground squirrels of Arizona is borrowed from Hoffmeister (1986).

Hoffmeister DF. 1986. Mammals of Arizona. Tucson (AZ, USA): University of Arizona Press.

1

Length of tail less than 25 percent of total length, first upper cheek tooth (Pm3) large, upper toothrows diverge anteriorly (distance across palate between Pm3's much greater than between M3s . . . . . 2

Length of tail more than 25 percent of total length, first upper cheek tooth (Pm3) peglike, upper toothrows nearly parrallel with distance across palate between Pm3's and M3's about the same . . . . . 3

Tail tipped with black, jugal heavy and thick, with outer surface at angle to ascending ramus presenting a broad triangular surface, greatest length of skull usually more than 60 mm... Black-tailed Prairie Dog (Cynomys ludovicianus)
Tail tipped with white or with top terminal part of tail with grayish or whittish center, jugal thin with outer surface at angle of ascending ramus only slightly thickened, the margin rounded and not distinctly triangular, greatest length of skull usually less than 60 mm... Gunnison's Prairie Dog (Cynomys gunnisoni)

Gunnison's Prairie Dog (Cynomys gunnisoni) observed by Cathy Pasterczyk in Taos, New Mexico.
Black-tailed Prairie Dog (Cynomys ludovicianus) observed by Liam Pentangelo in Boulder County, Colorado.

Upper parts with a series of more than 10 longitudinal white stripes or rows of nearly connected white spots on a background of brown, postorbital processes weak.... Thirteen-lined Ground Squirrel (Ictidomys tridecemlineatus)

Upper parts plain, spotted, or mottled, or if with stripes, never more than two white stripes, postorbital processes small but prominent . . . . . 4

Tail long (more than 150 mm) and bushy; hind foot long (more than 48 mm); skull large, with greatest length more than 53 mm and upper toothrow more than 10.0 mm... Common Rock Squirrel (Otospermophilus variegatus)

Common Rock Squirrel (Otospermophilus variegatus) observed by Tim Healy at the Grand Canyon in Arizona.

Tail shorter than 150 mm and not especially bushy, hind foot shorter than 48 mm, skull with greatest length less than 50 mm and upper toothrow shorter than 10.0 mm . . . . . 5

One white stripe on each side and tail relatively broad or bushy . . . . . 7

Upper parts with numerous, whitish spots (but may be nearly absent if fur is badly worn), tail shorter and with more flattened appearance, bullae less inflated... Spotted Ground Squirrel (Xerospermophilus spilosoma)
Upper parts uniform in color and not spotted, tail longer and with more rounded appearance, auditory bullae more inflated... Round-tailed Ground Squirrel (Xerospermophilus tereticaudus)

Spotted Ground Squirrel (Xerospermophilus spilosoma) photographed by mnwild in southeastern Arizona.
Round-tailed Ground Squirrel (Xerospermophilus tereticaudus) photographed by Eric CLeveland in Twentynine Palms, California.

Reddish coloration on sides above front legs, tail bordered with reddish-brown, skull large, and upper toothrow more than 8.0 mm... Common Golden-mantled Ground Squirrel (Callospermophilus lateralis)

Common Golden-mantled Ground Squirrel (Callospermophilus lateralis) photographed by Rick Overson on Mount Howard, Oregon.

Coloration on sides above front legs tan or cinnamon, tail bordered with white, skull small, and upper toothrow usually less than 8.0 mm . . . . . 8

Underside of tail white, tail short, auditory bullae more inflated... White-tailed Antelope Squirrel (Ammospermophilus leucurus)
Underside of tail blackish, tail long, auditory bullae less inflated... Harris's Antelope Squirrel (Ammospermophilus harrisii)

White-tailed Antelope Squirrel (Ammospermophilus leucurus) photographed by lonnyholmes in Clark County, Nevada.
Harris's Antelope Squirrel (Ammospermophilus harrisii) photographed by Craig Robson in Pima County, Arizona.