Xerospermophilus spilosoma

Spotted Ground Squirrel
(*Xerospermophilus spilosoma*)
Spotted Ground Squirrel (Xerospermophilus spilosoma)
Range
Taxonomic classification
Order:	Rodentia
Suborder:	Sciuromorpha
Family:	Sciuridae
Subfamily:	Xerinae
Tribe:	Marmotini
Genus:	Xerospermophilus
Binomial details
	Xerospermophilus spilosoma (E. T. Bennett, 1833)
Other resources
	Full taxonomic details at MDD

The Spotted Ground Squirrel (Xerospermophilus spilosoma) is a small ground squirrel generally found in areas with deep sandy soils and sparse vegetation (Streubel and Fitzgerald, 1978).

Description

From Schmidly and Bradley (2016): "A small ground squirrel with scattered, more or less squarish, light spots on back (spots not in rows as in I. parvidens and I. tridecemlineatus); ears inconspicuous; tail about one-third of total length, pinkish buff or cinnamon buff beneath; upperparts smoke gray, light drab, or fawn color, the white spots small and obsolete, especially on shoulder; underparts white."

Museum specimens

Holotype: 17659/24595. Xerospermophilus spilosoma pratensis. Adult female. Pine plateau at north foot of San Francisco Mountain (Peaks), Coconino County, Arizona. Collected 5 August 1889.
Holotype: USNM 30410/42396. Xerospermophilus spilosoma annectens. Young adult male. Padre Island, Cameron County, Texas. Collected 24 August 1891.
Holotype: USNM 16750/23663. Xerospermophilus spilosoma canescens. Adult female. Oracle, Pinal County, Arizona. Collected 11 June 1889.
Holotype: USNM 17676/24612. Xerospermophilus spilosoma cryptospilotus. Adult male. Painted Desert, Coconino County, Arizona. Collected 17 August 1889.
Holotype: USNM 17116/24049. Xerospermophilus spilosoma major. Adult female. Albuquerque, Bernalillo County, New Mexico. Collected 22 July 1889.

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
Colorado	Armstrong et al. (2010)	200–245	50–80	28–35	6–8	100–200
Texas	Schmidly & Bradley (2016)	214	65	32		100–125

Skull

Holotype: 17659/24595. Xerospermophilus spilosoma pratensis. Adult female. Pine plateau at north foot of San Francisco Mountain (Peaks), Coconino County, Arizona. Collected 5 August 1889. Dorsal view of the skull.
Holotype: USNM 17659/24595. Xerospermophilus spilosoma pratensis. Adult female. Pine plateau at north foot of San Francisco Mountain (Peaks), Coconino County, Arizona. Collected 5 August 1889. Ventral view of the skull.
Holotype: USNM 17659/24595. Xerospermophilus spilosoma pratensis. Adult female. Pine plateau at north foot of San Francisco Mountain (Peaks), Coconino County, Arizona. Collected 5 August 1889. Lateral view of the skull.
Holotype: USNM 17659/24595. Xerospermophilus spilosoma pratensis. Adult female. Pine plateau at north foot of San Francisco Mountain (Peaks), Coconino County, Arizona. Collected 5 August 1889. Dorsal view of the mandible.
Holotype: USNM 17659/24595. Xerospermophilus spilosoma pratensis. Adult female. Pine plateau at north foot of San Francisco Mountain (Peaks), Coconino County, Arizona. Collected 5 August 1889. Lateral view of the left mandible.

Similar species

Comparison with Ictidomys parvidens and Ictidomys tridecemlineatus

The spotting pattern in Xerospermophilus spilosoma is not in rows as in the Rio Grande Ground Squirrel (Ictidomys parvidens) and Thirteen-lined Ground Squirrel (Ictidomys tridecemlineatus). Ictidomys parvidens is more similar in appearance to X. spilosoma, but it has a much longer and bushier tail.

Spotted Ground Squirrel (Xerospermophilus spilosoma) photographed by mnwild in southeastern Arizona.
Rio Grande Ground Squirrel (Ictidomys parvidens) photographed by Alex Lamoreaux in Starr County, Texas.
Thirteen-lined Ground Squirrel (Ictidomys tridecemlineatus) photographed by Zoë Unruh in Saskatchewan, Canada.

Comparison with Xerospermophilus tereticaudus

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."

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.

References

Armstrong DM, Fitzgerald JP, Meaney CA. 2010. Mammals of Colorado, Second Edition. Denver (CO, USA): University Press of Colorado.

Bennett ET. 1833-05-17. Specimens were exhibited of numerous Mammalia recently obtained by the Society from that part of California which adjoins to Mexico. Proceedings of the Zoological Society of London 1833:39-42.

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

Schmidly DJ, Bradley RD. 2016. The mammals of Texas. Austin (TX, USA): University of Texas Press.

Streubel DP, Fitzgerald JP. 1978. Spermophilus spilosoma. Mammalian Species (101):1-4.