|Scientific Name:||Thomomys bulbivorus|
|Species Authority:||(Richardson, 1829)|
|Taxonomic Notes:||This species exhibits a genetic pattern of limited inbreeding within populations and much differentiation among populations; pattern reflects a cataclysmic event affecting the entire geographic distribution of the species about 13,000 years ago (Carraway and Kennedy 1993).|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor/s:||Linzey, A.V. & NatureServe (Hammerson, G.)|
|Reviewer/s:||Amori, G. (Small Nonvolant Mammal Red List Authority) & Chanson, J. (Global Mammal Assessment Team)|
Listed as Least Concern, although its extent of occurrence is less than 20,000 km², it is common within its range and its populations are not currently in decline, and it is reasonably adaptable to disturbance of its habitat.
|Range Description:||The species' range is restricted to the Willamette Valley, in Oregon in the United States, and to drainages of tributaries (especially the Yamhill River) to the Willamette River system; its range corresponds almost exactly with the extent of the Bretz Flood, which occurred about 13,000 years ago (Verts and Carraway, 1998). Its elevational range rarely exceeds 120 m asl (Verts and Carraway, 1998).|
Native:United States (Oregon)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The total adult population size is unknown but likely exceeds 100,000. Density at a few sample sites was crudely estimated at about 10 to about 32 per hectare (Verts and Carraway, 1998). Verts and Carraway (1998) mapped several dozen collection sites, most of which might be regarded as distinct occurrences (subpopulations). Presumably at least several occurrences have good viability. Area of occupancy, number of subpopulations, and population size probably are declining, but the rate of decline is unknown. Area of occupancy, number of subpopulations, and population size presumably have been reduced to some degree as a result of conversion of habitat to intensive human uses.|
|Habitat and Ecology:||
This pocket gopher is associated with early seral plant communities or cultivated areas that resemble such situations, including weedy lawns, land disturbed by clearing, fields of alfalfa, wheat, or oats, or filbert orchards, often in deep, heavy clay soils (Verts and Carraway, 1998). It avoids wetlands and poorly drained grassy fields (Verts and Carraway, 1998). It occurs in unwooded areas in hilly areas and lowlands and is common in agricultural and pastoral lands (Patton, in Wilson and Ruff, 1999). As is true of other pocket gophers, habits are mainly fossorial, with some surface activity. Breeds March to July. Gestation lasts probably about 18 or 19 days. Females produce one litter of three to five young per year. Young are born in April to July, weaned by six weeks. Presumably attains sexual maturity by the breeding season after birth.
Diet includes roots and tubers of false dandelion, vetch, fruit and nut trees, root crops, plantains, and grasses. Forages mainly within underground burrow, eats some surface vegetation. Carries food in external cheek pouches to underground storage areas. This species is primarily solitary (males enter burrows of females during breeding season). Predators include owls, hawks, coyotes, and foxes. Individuals rarely live more than three years in the wild. Pocket gophers are ecologically important as prey items and in influencing soils, microtopography, habitat heterogeneity, diversity of plant species, and primary productivity (Huntly and Inouye, 1988). This species is active throughout the year; it does not hibernate.
|Major Threat(s):||Habitat has been and continues to be altered via urbanization and conversion to intensive agriculture. Locally, in orchards and fields, this species is regarded as an agricultural pest and is subject to attempted eradication through poisoning and trapping. Based on the recovery of populations subject to trapping, Verts and Carraway (1998) concluded that this species can recover rapidly from periods of high mortality.|
|Conservation Actions:||At present this species is not of conservation concern, and its range probably includes a few protected areas.|
Carraway, L. N. and Kennedy, P. K. 1993. Genetic variation in Thomomys bulbivorus, an endemic to the Willamette Valley, Oregon. Journal of Mammalogy 74: 952-962.
Huntly, N. and Inouye, R. 1988. Pocket gophers in ecosystems: patterns and mechanisms. BioScience 38: 386-793.
Verts, B. J. and Caraway, L. N. 1987. Thomomys bulbivorus. Mammalian Species 273: 1-4.
Wilson, D. E. and Ruff, S. 1999. The Smithsonian Book of North American Mammals. Smithsonian Institution Press, Washington, DC, USA.
|Citation:||Linzey, A.V. & NatureServe (Hammerson, G.) 2008. Thomomys bulbivorus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 24 May 2013.|
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