Ictidomys parvidens

Rio Grande Ground Squirrel
(*Ictidomys parvidens*)
Rio Grande Ground Squirrel (Ictidomys parvidens)
Range
Taxonomic classification
Order:	Rodentia
Suborder:	Sciuromorpha
Family:	Sciuridae
Subfamily:	Xerinae
Tribe:	Marmotini
Genus:	Ictidomys
Binomial details
	Ictidomys parvidens (Mearns, 1896)
Other resources
	Full taxonomic details at MDD

Rio Grande Ground Squirrel (Ictidomys parvidens) is a medium-sized ground squirrel that occupies grassy habitats and grassy shrublands.

Description

From Schmidly and Bradley (2016): "A rather small ground squirrel with usually nine rows of squarish white spots on back; tail about two-fifths of total length, moderately bushy; ears short and rounded; upperparts wood brown or buffy brown with rows of conspicuous white spots; sides and underparts whitish or pinkish buff."

Museum specimens

Holotype: USNM 63073. Ictidomys parvidens. Adult male. Fort Clark, Kinney County, Texas. Collected 21 March 1893.
Holotype: USNM 63073. Ictidomys parvidens. Adult male. Fort Clark, Kinney County, Texas. Collected 21 March 1893.
Holotype: USNM 63073. Ictidomys parvidens. Adult male. Fort Clark, Kinney County, Texas. Collected 21 March 1893.

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
Texas	Schmidly & Bradley (2016)	301	118	41		males: 227–330; females: 137–198

Skull

Holotype: USNM 63073. Ictidomys parvidens. Adult male. Fort Clark, Kinney County, Texas. Collected 21 March 1893. Dorsal view of the skull. Note that the top of the cranium is damaged.
Holotype: USNM 63073. Ictidomys parvidens. Adult male. Fort Clark, Kinney County, Texas. Collected 21 March 1893. Ventral view of the skull.
Holotype: USNM 63073. Ictidomys parvidens. Adult male. Fort Clark, Kinney County, Texas. Collected 21 March 1893. Lateral view of the skull.
Holotype: USNM 63073. Ictidomys parvidens. Adult male. Fort Clark, Kinney County, Texas. Collected 21 March 1893. Dorsal view of the mandible.
Holotype: USNM 63073. Ictidomys parvidens. Adult male. Fort Clark, Kinney County, Texas. Collected 21 March 1893. Lateral view of the left mandible.

Similar species

Comparison with Ictidomys tridecemlineatus

From Stangl Jr. et al. (2012): "the two are superficially distinctive. The thirteen-lined ground squirrel is the smaller sciurid, seldom weighing in excess of 150 g. The dark dorsal pelage is marked by rows of white spots against a dark dorsum, with the spots of alternate rows confluent to form solid stripes. The Rio Grande ground squirrel is a larger and heavier animal that can exceed 300 g, and sports both a proportionally longer tail and series of distinct spots arranged in rows against a comparatively pale tan-to-gray dorsum."

Thompson (2013) provided "strong evidence for contemporary hybridization between I. parvidens and the Thirteen-lined Ground Squirrel (Ictidomys tridecemlineatus) in southeastern New Mexico and western Texas."

Rio Grande Ground Squirrel (Ictidomys parvidens) photographed by Alex Lamoreaux in Starr County, Texas. A small ground squirrel with a long and moderately bushy tail, ears short and rounded, and upperparts with rows of conspicuous white spots.
Thirteen-lined Ground Squirrel (Ictidomys tridecemlineatus) photographed by Zoë Unruh in Saskatchewan, Canada. A small ground squirrel with a relatively short tail that lacks fluff, ears short and rounded, and a dorsum usually with 13 alternating dark and light stripes. The dark stripes contain a series of squarish or buffy spots.
Distribution of the Rio Grande Ground Squirrel (Ictidomys parvidens) and the Thirteen-lined Ground Squirrel (Ictidomys tridecemlineatus) and presumed area of sympatry. Circles represent the locations where individuals were morphologically or genetically identified as either species or as hybrids by Thompson et al. (2013).

References

Mearns EA. 1896-03-25. Preliminary diagnoses of new mammals from the Mexican border of the United States. Proceedings of the United States National Museum 18:443-447.

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

Thompson C. 2013. Implications of hybridization between the Rio Grande ground squirrel (Ictidomys parvidens) and the thirteen-lined ground squirrel (I. tridecemlineatus). [dissertation]. [Lubbock (TX, USA)]: Texas Tech University.