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Camas pocket gopher
The camas pocket gopher (''Thomomys bulbivorus''), also known as the camas rat or Willamette Valley gopher, is a rodent, the largest member in the genus ''Thomomys'', of the family Geomyidae. First described in , it is endemic to the Willamette Valley of northwestern Oregon in the United States. The herbivorous gopher forages for vegetable and plant matter, which it collects in large, fur-lined, external cheek pouches. Surplus food is hoarded in an extensive system of underground tunnels. The dull-brown-to-lead-gray coat changes color and texture over the year. The mammal's characteristically large, protuberant incisors are well adapted for use in tunnel construction, particularly in the hard clay soils of the Willamette Valley. The gophers make chattering sounds with their teeth; males and females make purring (or crooning) sounds when they are together, and the young make twittering sounds. Born toothless, blind and hairless, the young grow rapidly before being weaned at about six weeks of age.
Although the camas pocket gopher is fiercely defensive when cornered, it may become tame in captivity. While population trends are generally stable, threats to the species' survival include urbanization, habitat conversion for agricultural use and active attempts at eradication with trapping and poisons. It is prey for raptors and carnivorous mammals, and host to several parasitic arthropods and worms. Scientists believe that the gopher's evolutionary history was disrupted when the Missoula Floods washed over the Willamette Valley at the end of the last ice age. The floods almost completely inundated its geographic range, which may have caused a genetic bottleneck as survivors repopulated the region after the waters receded.
==Taxonomy==
There are six genera of North American pocket gophers: ''Cratogeomys'', ''Geomys'', ''Orthogeomys'', ''Pappogeomys'', ''Thomomys'', and ''Zygogeomys''. The camas pocket gopher is a smooth-toothed pocket gopher of the genus ''Thomomys'', within the pocket-gopher family Geomyidae. The incisors of gophers in the genus ''Thomomys'' have characteristically smooth anterior surfaces, while those of ''Geomys'' have two deep grooves per tooth and those of ''Cratogeomys'' have a single groove. The camas pocket gopher is a member of the subgenus ''Megascapheus'', established in 1903, at that time for the camas pocket gopher alone. Taxonomists subsequently assigned other gophers to the same subgenus. The name ''Thomomys'' derives from the Greek ''σωρός'' (heap) + ''μῦς'' (mouse), probably describing the mounds of excavated soil produced by the burrowing gopher. ''Bulbus'' translates as "bulb" in Latin, and the word for "devour" is ''voro''. Naturalist David Douglas reported that the gopher consumed bulbs of the camas lily, and Vernon Bailey later attributed the lack of camas lilies in areas inhabited by the gopher to the bulbs being eaten. However, naturalist H. M. Wight observed that the gopher ate primarily dandelion greens, and was skeptical that it was a large consumer of bulbs.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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