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Xerospermophilus tereticaudus

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Round-tailed Ground Squirrel
(Xerospermophilus tereticaudus)
Range
Taxonomic classification
Order:Rodentia
Suborder:Sciuromorpha
Family:Sciuridae
Subfamily:Xerinae
Tribe:Marmotini
Genus:Xerospermophilus
Binomial details
Xerospermophilus tereticaudus (S. F. Baird, 1857)
Other resources
Full taxonomic details at MDD

The Round-tailed Ground Squirrel (Xerospermophilus tereticaudus) is a small ground squirrel that occupies the deserts of the southwestern United States and northwestern Mexico.

Description

From Hoffmeister (1986): "Size small to medium; ears small; tail not broadly haired, giving rounded appearance; dorsum light buff to dark cinnamon, a second color phase darker and grayer."

Round-tailed Ground Squirrel (Xerospermophilus tereticaudus) photographed by Eric CLeveland in Twentynine Palms, California.
Round-tailed Ground Squirrel (Xerospermophilus tereticaudus) photographed by Aaron Graham in Phoenix, Arizona.

Museum images

  • Holotype: USNM 186470. Xerospermophilus tereticaudus neglectus. Adult male. The valley 1 mi (1.6 km) west of Dolan’s Spring, Arizona. A. H. Howell (1938:187) interpreted this to be 12 mi (19 km) northwest of Chloride, Mohave County. Collected 9 February 1889. Dorsal view of the skin.
  • Holotype: USNM 186470. Xerospermophilus tereticaudus neglectus. Adult male. The valley 1 mi (1.6 km) west of Dolan’s Spring, Arizona. A. H. Howell (1938:187) interpreted this to be 12 mi (19 km) northwest of Chloride, Mohave County. Collected 9 February 1889. Ventral view of the skin.

External measurements

Length measurements are in millimeters (mm) and weight measurements are in grams (g), unless stated otherwise. If available, the sample size (n=) is provided. If a range is not provided and n= is not given, then the listed measurement represents an average.

Part of range Reference Total length Tail length Hindfoot length Ear length Mass
California Jameson & Peeters (2004) 204–266 60–107 32–40 5–6 116–133


Skull

  • Holotype: USNM 186470. Xerospermophilus tereticaudus neglectus. Adult male. The valley 1 mi (1.6 km) west of Dolan’s Spring, Arizona. A. H. Howell (1938:187) interpreted this to be 12 mi (19 km) northwest of Chloride, Mohave County. Collected 9 February 1889. Dorsal view of the skull. The tip of the nasal bones are broken in this specimen.
  • Holotype: USNM 186470. Xerospermophilus tereticaudus neglectus. Adult male. The valley 1 mi (1.6 km) west of Dolan’s Spring, Arizona. A. H. Howell (1938:187) interpreted this to be 12 mi (19 km) northwest of Chloride, Mohave County. Collected 9 February 1889. Ventral view of the skull. The tip of the nasal bones are broken in this specimen.
  • Holotype: USNM 186470. Xerospermophilus tereticaudus neglectus. Adult male. The valley 1 mi (1.6 km) west of Dolan’s Spring, Arizona. A. H. Howell (1938:187) interpreted this to be 12 mi (19 km) northwest of Chloride, Mohave County. Collected 9 February 1889. Lateral view of the skull.
  • Holotype: USNM 186470. Xerospermophilus tereticaudus neglectus. Adult male. The valley 1 mi (1.6 km) west of Dolan’s Spring, Arizona. A. H. Howell (1938:187) interpreted this to be 12 mi (19 km) northwest of Chloride, Mohave County. Collected 9 February 1889. Dorsal view of the mandible. The right mandible is broken and incomplete.
  • Holotype: USNM 186470. Xerospermophilus tereticaudus neglectus. Adult male. The valley 1 mi (1.6 km) west of Dolan’s Spring, Arizona. A. H. Howell (1938:187) interpreted this to be 12 mi (19 km) northwest of Chloride, Mohave County. Collected 9 February 1889. Lateral view of the left mandible.

Similar species

Comparison with Xerospermophilus mohavensis

From Best (1995): "Compared with tereticaudus, mohavensis is most easily distinguished by its tail, which has a white undersurface, is shorter, and is more broadly haired (flatter) than in tereticaudus. Claws of mohavensis are stouter, cheeks are brownish instead of white, quantity of winter pelage is greater, and general tone of coloration always is decidedly dark (Grinnell and Dixon, 1918). [Xerospermophilus] mohavensis also is significantly larger than tereticaudus in 18 of 20 cranial characters (except postorbital and interorbital breadths)." See Leitner (2015) for more detailed information on where the two species co-occur in California.

  • Round-tailed Ground Squirrel (Xerospermophilus tereticaudus) observed by dumplingbug in Pima County, Arizona. Notice the that the underside of the tail is tan.
  • Mohave Ground Squirrel (Xerospermophilus mohavensis) observed by Venkat Sankar in San Bernardino County, California. Notice the that the underside of the tail is creamy white.
  • Range of the Mohave Ground Squirrel (Xerospermophilus mohavensis) (purple) and the Round-tailed Ground Squirrel (Xerospermophilus tereticaudus) (green). These two species are sympatric (co-occur) in San Bernardino County, California.

Comparison with Xerospermophilus spilosoma

From Hoffmeister (1986): "The spotting pattern distinguishes spilosoma from tereticaudus. Indistinctly spotted spilosoma can be distinguished from tereticaudus by a shorter, flatter tail. Cranially, spilosoma can be distinguished from tereticaudus by a more rounded braincase when viewed posteriorly and less inflated bullae."

References

Baird SF. 1857. General Report upon the Zoology of the Several Pacific Railroad Routes. Part I. Mammals. A. P. Nicholson, Washington, 757 pp.

Ernest KA, Mares MA. 1987. Spermophilus tereticaudus. Mammalian Species (274):1-9.

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

Jameson EW, Peeters HJ. 2004. Mammals of California (No. 66). Berkeley (CA, USA): University of California Press.

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