Thomomys mazama Merriam 1897

2. Western Pocket Gopher Thomomys mazama French: Gaufre du Mazama / German: Mazama-Taschenratte / Spanish: Tuza occidental Other common names: Mazama Pocket Gopher; Puget Sound Pocket Gopher (pugetensis), Tacoma Pocket Gopher (tacomensis) Taxonomy. Thomomys mazama Merriam, 1897, “Crater Lake, Mt. Mazama, [Klamath County] Oregon,” USA. Placed into subgenus Thomomys. Formerly regarded: as a subspecies of 1. monticola. Subspecies tacomensis, named by W. P. Taylor in 1919, known only from the vicinity of Tacoma, Pierce County, Washington,is probably extinct as a result of urban expansion. Fourteen extant subspecies recognized. Subspecies and Distribution. T.m.mazamaMerriam,1897—CascadeRange,fromCOregonthroughNCalifor- nia,USA. T.m.couchiGoldman,1939—vicinityofShelton,MasonCounty,Washington,USA. T.m.glacialisDalquest&Scheffer,1942—RoyPrairie,PierceCounty,Washington,USA. T.m.helleriElliot,1903—mouthoftheRogueRiver,CurryCounty,Washington,USA. T.m.hesperusMerriam,1901—coastalrangesofNWOregon,USA. T.m.lowieiGardner,1950—NECathlamet,WahkiakumCounty,Washington,USA. T.m.melanopsMerriam,1899—OlympicMts,ClallamCounty,Washington,USA. T.m.nasicusMerriam,1897—DeschutesRiverregion,COregon,USA. T.m.nigerMerriam,1901—coastofCOregon,USA. T.m.oregonusMerriam,1901—N&NWedgeofWillametteValley,Oregon,USA. T.m.premaxillarisGrinnell,1914—YollaBollyMts,TehamaCounty,California,USA. T.m.pugetensisDalquest&Scheffer,1942—vicinityofOlympia,ThurstonCounty,Washington,USA. T.m.tumuliDalquest&Scheffer,1942—NofTenino,ThurstonCounty,Washington,USA. T. m. yelmensis Merriam, 1899 — vicinity of Yelm Prairie, Thurston County, Washington, USA. Descriptive notes. Head-body 140-170 mm, tail 50-80 mm; weight 80-130 g. Male Western Pocket Gophers are slightly larger than females. This medium-sized pocket gopher has a fusiform body shape typical of all pocket gophers, and it possesses furlined cheek pouches that open external to the mouth. It is reddish brown dorsally, although some individuals, even entire populations, are completely melanistic. The Western Pocket Gopher can be distinguished from most nearby species of pocket gophers by its unusually large post-auricular patches, which are 5-6 times the area of the ear. The Western Pocket Gopher can be distinguished from the Northern Pocket Gopher (T. talpoides) by presence of an unusually long baculum in males (longest recorded for all geomyid species), often exceeding 22 mm in length. Bacula of the Northern Pocket Gopher rarely exceed 17 mm in length. The Western Pocket Gopher has a 2n = 40-58 karyotype. Habitat. Alpine meadows, open park-like habitats, glacial prairies, pastures, savannas, and early seral woodlands and forests where soils are deep silt or sandy loams. Mixedconifer forests often dominate habitats used by Western Pocket Gophers. Food and Feeding. Consumption of plant species by the Western Pocket Gopher corresponds quite well with relative availabilities of those plant species. Annual diet consists primarily of grasses, roots of woody plants, and forbs. As in all 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. Surface feeding activity in the immediate vicinity of the borrow entrance has been reported for the Western Pocket Gopher. Feeding habits of the Western Pocket Gopher, particularly the numerous mounds of soil deposited on the surface, are believed by some researchers to have contributed to the formation of what are known as Mima mounds in prairie regions of Oregon and Washington in western USA. Mima mounds are conspicuous mounds of soil varying greatly in size but averaging c.600 cm in diameter and ¢.100 cm high that occur in dense clusters and cover large areas of prairie habitat. Mounds are approximately evenly spaced, and spacing is roughly equivalent to size of individual pocket gopher burrow systems. Pocket gophers no longer occupy the vast majority of Mima mounds. Breeding. The Western Pocket Gopher mates in spring, has a gestation of ¢.28 days, and has 1-7 young/litter. One study reported an average of 3-9 young/litter, which was the lowest average recorded among five species of Thomomys that occur in Oregon. Nest chambers excavated in southern Washington were ¢.25 cm in diameter and c.15 cm high at an average depth of c.90 cm below the surface. These nests were lined with dry grass. The Western Pocket Gopher was coprophagous in captivity, but coprophagy in wild individuals has not been investigated. Activity patterns. There is no specific information available for this species, but most species of pocket gopher can be active at any hour of the day with periods of peak activity usually around dawn and dusk. Movements, Home range and Social organization. The Western 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. In eastern Oregon, 110 Western Pocket Gophers were removed from a 4ha plot during a 14month period (= density of ¢.28 ind/ha), which did not account for possible immigration onto the plot from surrounding areas after residents were removed. In populations studied in Klamath County, Oregon, c.53% of individuals were young-of-the-year, 42% were 1-2 years old, and 5% were 2-3 years old. No individuals collected were older than c.3 years. Sex ratio in young-of-the-year was 1:1, but it was slightly female-biased in the older age classes. Status and Conservation. Classified as Least Concern on The IUCN Red List. Five subspecies of the Western Pocket Gopher (glacialis, pugetensis, tumuli, and yelmensis) are classified as threatened by the US Fish and Wildlife Service. Bibliography. Burton & Black (1978), Linzey & NatureServe (Hammerson) (2008s), Livezey & Verts (1979), Patton (1999e, 2005b), Taylor (1919), Thaeler (1980), USFWS (2015), Verts & Carraway (1998, 2000), Wilks (1962), Witmer etal. (1996).Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Geomyidae, pp. 234-269 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on pages 236-237, DOI: 10.5281/zenodo.660380