Thomomys sheldoni Wied-Neuwied 1839

9.

Sierra Madre Occidental Pocket Gopher

Thomomys sheldoni

French: Gaufre de Sheldon / German: Sierra Madre-Taschenratte / Spanish: Tuza de Sierra Madre Occidental

Other common names: Sheldon Pocket Gopher

Taxonomy. Thomomys sheldoni Bailey, 1915,

“Santa Teresa (6,800 feet altitude), Tepic, [Nayarit], Mexico.”

Placed into subgenus Megascapheus. Considered a subspecies of T. umbrinus by E. W. Nelson and E. A. Goldman in 1934, and a junior synonym of T. u. madrensis by J. L. Patton in 2005. Resurrected to species status by V. L. Mathis and colleagues in 2013. Molecular studies show T. sheldoni to be a member of the T. umbrinus species group, which includes 7. umbrinus, T. atrovarius, T. sheldoni, and T. nayarensis. Two subspecies recognized.

Subspecies and Distribution.

T.s.sheldoniBailey,1915—WDurango,WZacatecas,andNENayarit,Mexico.

T. s. chihuahuae Nelson & Goldman, 1934 — NC Chihuahua, Mexico.

Descriptive notes. Head-body 120-180 mm, tail 55-80 mm, hindfoot 23-30 mm; weight 75-130 g. Male Sierra Madre Occidental Pocket Gophers are slightly larger than females. This mediumsized pocket gopher has a fusiform body shape typical of all pocket gophers, and it possesses fur-lined cheek pouches that open external to the mouth. Its pelage is moderately dense and medium to dark brown dorsally, occasionally with a faint, slightly darker dorsal stripe. Ventral pelage is golden or yellowish brown. Female Sierra Madre Occidental Pocket Gophers have three pairs of mammae, one pectoral and two inguinal. Chromosomal complement has 2n = 76 and FN = 118-152.

Habitat. Restricted to upper elevation habitats (generally above 2000 m) with deep, friable soils that support pine-oak woodlands.

Food and Feeding. There is no specific information available for this species, but all pocket gophers that have been studied eat predominately underground roots and tubers and a limited amount of surface vegetation. As in all other pocket gophers, the burrow system is a series of shallow feeding tunnels radiating spoke-like from a deeper, central network that contains one or more nest chambers and several smaller chambers for storage of food or fecal pellets.

Breeding. There is no specific information available for this species, but breeding habits of the Sierra Madre Occidental Pocket Gopher are probably like those ofall other species of Thomomys, with 1-2 periods of peak breeding activity per year and 3-6 young/ litter.

Activity patterns. There is no specific information available for this species, but field studies suggest that the Sierra Madre Occidental Pocket Gopher is active at any hour of the day, with periods of peak activity around dawn and dusk. It does not hibernate and is active year-round.

Movements, Home range and Social organization. The Sierra Madre Occidental Pocket Gopher is solitary and aggressively territorial. Because it rarely leaves its burrow system,its home range is defined by size and extent of its burrow system. Field observations suggest that home range size is typical of that measured in other medium-sized pocket gophers, covering 30-80 m® of surface area.

Status and Conservation. The Sierra Madre Occidental Pocket Gopheris not listed on The IUCN Red List, but it is common throughoutits distribution and probably not threatened anywhere.

Bibliography. Bailey (1915), IUCN (2015d), Mathis et al. (2013a), Nelson & Goldman (1934), Patton (2005b).