Thomomys
| Genus Thomomys | |
|---|---|
| Range | |
 | |
| Taxonomic classification | |
| Order: | Rodentia |
| Suborder: | Supramyomorpha |
| Infraorder: | Castorimorphi |
| Superfamily: | Geomyoidea |
| Family: | Geomyidae |
| Subfamily: | Geomyinae |
| Tribe: | Thomomyini |
Pocket gophers are burrowing rodents in the family Geomyidae. They are cryptic species and can be very difficult to distinguish based on external morphological characters alone. Members in the genus Thomomys are referred to as the smooth-toothed claw-digging pocket gophers. Their upper incisors are smooth (lack grooves), which distinguishes them from the Yellow-faced Pocket Gopher (Cratogeomys castanops) and pocket gophers in the genus Geomys. Morphological differences between Thomomys and Megascapheus (another group of smooth-toothed gophers) is best explained by Álvarez-Castañeda and Segura-Trujillo (2025): "Morphological difference between Megascapheus in relation to Thomomys are: the upper incisors procumbent and their root between the fourth upper premolars and the first upper molars vs upper incisors not procumbent and their root above the fourth upper premolars; sphenoidal fissure open vs closed (except for some specimens of T. clusius); angular process continuous, with a well-developed flange along the ventral ramus side vs not continuous, with a weakly developed flange along the ventral ramus side; rostrum heavy vs rostrum slender; base of the first lower premolars inclined anteriorly vs nearly perpendicular to the occlusal surface of the toothrow; infraorbital canal openings anterior to the incisive foramina vs directly above or slightly posterior to the incisive foramina; anterior enamel plate of the first lower premolars not recurved vs recurved, frequently forming a shallow re-entrant angle; anterior enamel plate of the first lower premolars narrow and broadly separated from the lateral enamel plate on the lingual side, vs only slightly separated from the posterior enamel plate (rarely continuous), with the lateral enamel plate on the lingual side; chromosome number of living forms from 74 to 82 vs from 40 to 60 (Nelson and Goldman 1934; Russell 1968; Álvarez-Castañeda 2024)."
There are five species in the genus Thomomys and all can be found in the United States.
Species
Key to the species of Thomomys
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Dorsal view of a Idaho Pocket Gopher (Thomomys idahoensis) collected in 1890 in Lemhi County, Idaho. Dorsal color is variable ranging from yellowish brown with hair tipped with a dark brown to grayish brown or a dark brown. Venter is light gray and often suffused with yellowish or yellowish brown. This species lacks completely, or nearly so, any dark periauricular patches. The feet are whitish and the tail coloration is variable. Incisors are smooth and lack grooves. -
Wyoming Pocket Gopher (Thomomys clusius) photographed by Britt Brito. © Britt Brito. Pelage is pale, yellowish-gray with slight brownish tinge. The venter, foot, and tail are white, but the snout is blackish. Incisors are smooth and lack grooves. -
Dorsal view of a Western Pocket Gopher (Thomomys mazama) collected in 1896 in Klamath County, Oregon. Coloration is variable. Nose and face usually are dusky, plumbeous, or blackish; chin, feet, and tip of tail commonly are light gray, white, or buff; and the chest commonly contains white splotches. The dark patch of fur behind the ear is five to six times as large as the ear. Incisors are smooth and lack grooves. -
Dorsal view of a Mountain Pocket Gopher (Thomomys monticolus) collected in 1898 in Siskiyou County, California. Dull pale reddish brown above, strongly tinged with gray; below ashy white, sometimes with a faint tinge of buff; feet and tail whitish; no white throat spot; ears in a large blackish area. Incisors are smooth and lack grooves. -
Northern Pocket Gopher (Thomomys talpoides) photographed by ML Watson in Conejos County, Colorado. Color varies geographically from dark brown or yellow-brown to pale, grayish yellow. Chin is white and postauricular patches (area behind the ear) blackish or grayish black. The feet commonly are white or partly white. Incisors are smooth and lack grooves.
Taxonomic notes
Elevation of subgenera within genus Thomomys Wied-Neuwied, 1839
Genetic analyses (CytB and COI) by Álvarez-Castañeda and Segura-Trujillo (2025) found that the two subgenera within the genus Thomomys Wied-Neuwied, 1839 — Megascapheus and Thomomys — are genetically distinct. Morphological and genetic data support considering these differences sufficient at the genus level. Both subgenera Megascapheus and Thomomys were elevated to the taxonomic rank of genus by Álvarez-Castañeda and Segura-Trujillo (2025).
Available taxon pages
The following subgenera are available on WhiskerWiki for this genus:
- Subgenus: No information
Range maps
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Wyoming Pocket Gopher (Thomomys clusius) -
Idaho Pocket Gopher (Thomomys idahoensis) -
Western Pocket Gopher (Thomomys mazama) -
Mountain Pocket Gopher (Thomomys monticolus) -
Northern Pocket Gopher (Thomomys talpoides)
References
Álvarez-Castañeda ST. 2010. Phylogenetic structure of the Thomomys bottae–umbrinus complex in North America. Molecular Phylogenetics and evolution 54(3): 671-679.
Álvarez-Castañeda ST, Segura-Trujillo CA. 2025. Genus-level review of pocket gophers in the family Geomyidae. Therya 16(1):41-75.